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Air, Water, and Food 



FROM A SANITARY STANDPOINT 



BY 

ALPHEUS G. WOODMAN and JOHN F. NORTON 

A ssociate Professor of A ssistant Professor of 

Food A nalysis ■ Chemistry of Sanitation 

MASSACHUSETTS INSTITUTE OF TECHNOLOGY 



" These cannot be taken as sufficient ... in these times when 
every word spoken finds at once a ready doubter, if not an opponent. 
They are, however, specimens, and will serve to make comparisons 
in time to come." — Angus Smith. 

" The ideal scientific mind, therefore, must always be held in a 
state of balance which the slightest new evidence may change in one 
direction or another. It is in a constant state of skepticism, know- 
ing full well that nothing is certain." — Henry A. Rowland. 



FOURTH EDITION, REVISED AND REWRITTEN 
TOTAL ISSUE FIVE THOUSAND 



NEW YORK 

JOHN WILEY & SONS, Inc. 

London: CHAPMAN & HALL, Limited 

1914 



rb° 



^ 






Copyright, i960, 1904, 1909 

BY 

ELLEN H. RICHARDS and ALPHEUS G. WOODMAN 
Copyright, 19 14 

BY 

ALPHEUS G. WOODMAN and JOHN F. NORTON 



Stanbopc ipress 

H.GILSON COMPANY 
BOSTON. U.S.A. 



LC Control Number 



""/"- llil 

©CU387556 




+Lo 



tmp96 028457 



PREFACE 



Since the last edition (1909) of Air, Water, and Food was 
published there have been distinct advances in analytical meth- 
ods, and a changed point of view has brought about a somewhat 
different interpretation of results. This is particularly true 
with regard to the relation of air to health and comfort. At the 
present time the subject is still in a somewhat transitory state. 
In order that the book might remain useful it seemed necessary 
to make a careful revision of the whole. 

The death of one of the authors, Mrs. Ellen H. Richards, 
made a change in authorship necessary. We are indebted to 
Prof. R. H. Richards for permission to use any material from 
the former edition. While realizing that the book was first 
written from a " missionary" standpoint (Mrs. Richards' 
strong point), it actually has been used mainly for college and 
technical school teaching; consequently the character of part of 
the general discussion has been considerably changed. 

All of the discussion on air and water has been completely 

rewritten, as has the section on milk, the older methods revised, 

and numerous additions, to correspond with the latest practice, 

made. As in previous editions, these discussions are intended 

to be essentially elementary rather than exhaustive. 

A. G. W. 

J. F. N. 
Boston, July, 1914. 



CONTENTS 



Chapter ■ Page 

I. Three Essentials of Human Existence i 

II. Air and Health 9 

III. Air: Analytical Methods 21 

IV. Water: Its Relation to Health, Its Source and Properties.. 43 
V. Safe Water and the Interpretation of Analyses 56 

VI. Water: Analytical Methods 69 

VII. Food in Relation to Human Life, Definition, Sources, Classes, 

Dietaries in 

Vin. Adulteration and Sophistication of Food Materials 124 

IX. Analytical Methods 135 

Appendices 208 

Bibliography 228 



AIR, WATER, AND FOOD 



CHAPTER I 

THREE ESSENTIALS OF HUMAN EXISTENCE 

Air, water, and food are three essentials for healthful human 
life. Chemical Analysis deals with these three commodities in 
their relation to the needs of daily existence: first, as to their 
normal composition; second, as to natural variations from the 
normal; third, as to artificial variations — those produced 
directly by human agency with benevolent intention, or result- 
ing from carelessness or cupidity. A large portion of the prob- 
lems of public health come under these heads, and a discussion 
of them in the broadest sense includes a consideration of engi- 
neering questions and of municipal finances. This, however, is 
beyond the scope of the present work. 

The following pages will deal chiefly with such portions of 
the Chemistry of Sanitation as come directly under individual 
control, or which require the education of individuals in order 
to make up the mass of public opinion which shall support the 
city or state in carrying out sanitary measures. 

A notable interest in the subject of individual health as a 
means of securing the highest individual capacity both for 
work and for pleasure is being aroused as the application of 
the principles governing the evolutionary progress of other 
forms of living matter is seen to extend to mankind. 

Will power may guide human forces in most economical 
ways, and may concentrate energy upon a focal point so as 
to seem to accomplish superhuman feats, but it cannot create 
force out of nothing. There is a law of conservation of human 



2 AIR, WATER, AND FOOD 

energy. The human body, in order to carry on all its functions 
to the best advantage, especially those of the highest thought 
for the longest time, must be placed under the best conditions 
and must be supplied with clean air, safe water, and good food, 
and must be able to appropriate them to its use. The day is 
not far distant when a city will be held as responsible for the 
purity of the air in its schoolhouses, the cleanliness of the water 
in its reservoirs, and the reliability of the food sold in its markets 
as it now is for the condition of its streets and bridges. Nor 
will the years be many before educational institutions will be 
held as responsible for the condition of the bodies as of the 
minds of the pupils committed to their care; when a chair of 
Sanitary Science will be considered as important as a chair 
of Greek or Mathematics; when the competency of the food- 
purveyor will have as much weight with intelligent patrons as 
the scholarly reputation of any member of the Faculty. Within 
a still shorter time will catalogues call the attention of the inter- 
ested public to the ventilation of college halls and dormitories, 
as well as to the exterior appearance and location. 

These results can be brought about only when the students 
themselves appreciate the possibilities of increased mental produc- 
tion under conditions of decreased friction, such as can be found 
only when the requirements of health are perfectly fulfilled. 

Of the three essentials, air may well be considered first, al- 
though its office is to convert food already taken into heat and 
energy. Its exclusion only for a few minutes causes death, and 
in quantity used it far exceeds the other two. Again, so im- 
portant is the action of air that the quality of food is of far less 
consequence when abundant oxygen is present, as in pure air, 
than when it is present in lessened quantity, as in air vitiated 
by foreign substances. 

Individual habit has much to do with the appreciation of 
good air, and as our knowledge of the value of an abundance of 
this substance in securing great efficiency in the human being 
increases, we shall be led to attach more importance to the 
sufficiency of the supply. 



THREE ESSENTIALS OF HUMAN EXISTENCE 3 

In northern climates air is not free to all in the sense of cost- 
ing nothing, for the coming of fresh air into the house means 
an accompaniment of cold which must be counteracted by the 
consumption of fuel. A mistaken idea of economy leads house- 
holders, school boards, and college trustees to limit the size of 
the air-ducts as well as of the rooms. It is therefore necessary 
to emphasize the facts which science has fully established, in 
order to secure the survival of the fittest of the race under the 
present pressure of economic conditions, which take so little 
account of the highest welfare of the human machine. 

Air, water, and soil are the common possessions of man- 
kind. It is impossible for man to use either selfishly without 
injury to his neighbor and without squandering his inheritance. 
Primitive man could leave a given spot when the soil became 
offensive, and neighbors were then too few to require con- 
sideration; but neither man nor beast could with impunity foul 
the stream for his neighbor who had rights below him. The 
soil is permanent; one knows where to look for it and its pollu- 
tion. Air is abundant and is kept in constant motion by forces 
of nature beyond human control, so that, save in the neighbor- 
hood of an exceptionally offensive factory, man does not often 
foul the free air of heaven; it is only when he confines it within 
unwonted bounds that it becomes a menace. 

Water is the next precious commodity of the three. With- 
out it man dies in a few days; without it the soil is barren; 
without it air in motion parches all vegetation and carries 
clouds of dust particles; without it there is no life. As popu- 
lation increases it becomes necessary to collect as much of the 
rainfall as possible, to store it until needed, and to use it with 
discretion. After use it is often loaded with impurities and sent 
to deal death and destruction to those who require it later, and 
yet, in nature's plan, it is the carrier of the world, and rightly 
treated and carefully husbanded there is enough for the needs of 
all. Its presence or absence has been the controlling force in 
determining the habitations of men. In its office of carrier it 
not only brings nourishment in solution to the tissues of the 



4 AIR, WATER, AND FOOD 

human body, but also carries away the refuse material. It is a 
cardinal principle in all sanitary reforms to get rid of that which 
is useless as soon as possible. Too little water allows accumu- 
lation of waste material and a clogging of the bodily drainage 
system. 

The average quantity needed daily by the human body is 
about three quarts. Of this a greater or less proportion is taken 
in food, so that at times only from a pint to a quart need be 
taken in the form of water as such. 

Next in importance to quantity is the quality, dependent 
somewhat upon the uses to which it is to be put. As a rule, 
the moderately soft waters are the best for any purpose. For 
drinking purposes water must be free from dangers to health in 
the way of poisonous metals, decomposing matters, and disease- 
germs. For domestic use economy requires that it should not 
decompose too much soap. Manufacturing interests require 
that it should not give too much scale to boilers; for agriculture 
there should not be too much alkali. 

From the nature of things, no one family or city can have 
sole control of a given body of water. Those on the highlands 
may have the first use of the water, which then percolates to a 
lower level and is used by the people on the slopes over and 
over before it reaches the sea to start again on its cycle of vapor, 
cloud and rain, brook and river. Although receiving impurities 
each time, there are many beneficent influences at work to 
overcome the evils resulting from this repeated use. That 
which is dissolved from one portion of earth may be deposited 
on another. As the plant is the scavenger of the air, withdraw- 
ing the carbon dioxide with which it would otherwise become 
loaded, so the water has also its plant life, purifying it and 
withdrawing that which would otherwise soon render it unfit 
for any use. 

Pure water is found only in the chemical laboratory; the most 
that can be hoped for is that human beings may secure for them- 
selves water which is safe to drink, which will not impair the 
efficiency of the human machine. 



THREE ESSENTIALS OF HUMAN EXISTENCE 5 

The importance of the third essential for human life, food, 
and the close interdependence of all three, may be clearly shown. 
Of little use is it to provide pure air and clean water if the sub- 
stances eaten are not capable of combining with the oxygen of 
the air or of being dissolved in the water or the digestive juices; 
of less use still is it to partake of substances which act as irri- 
tants and poisons on the tissues which they should nourish, and 
thus prevent healthful metabolism and respiratory exchange. 

And yet a large majority of those who have acquired some 
notion of the meaning and importance of pure air and are be- 
ginning to consider it worth while to strive for clean water pay 
not the least attention to the sanitary qualities of food; the 
palatable and aesthetic aspects only appeal to them. 

Steam-power is produced by the combustion of coal or oil. 
Human force is derived by releasing the stored energy of the 
food in the body. The delicately balanced mechanism of the 
human body suffers even more from friction than the most 
sensitive machine, and the greatest loss of potential human 
energy occurs through ignorance, carelessness, and reckless dis- 
regard of nature's laws in regard to food. 

It is necessary to know, first, what is the normal compo- 
sition of a given food-material. This is found by analyses of 
many typical samples. Second, is the sample under consider- 
ation normal? To answer this requires an analysis of it, and a 
comparison of the results with standards. If it is not normal, 
in what way does it depart from the standard both in health- 
fulness and in quality? Third, if a food-substance is normal, 
what are its valuable ingredients and in what proportions are 
they to be used in the daily diet? 

In regard to meat, milk, and fish, the sanitary aspect for the 
chemist resolves itself into two questions: Is the substance so 
changed as to become a possible source of poisonous products? 
Or has anything in the nature of a preservative been added to 
it? If so, is it of a nature injurious to man? 

There is, however, a great range of quality in some of the 
most abundant foodstuffs, such as the cereals, especially in the 



AIR, WATER, AND FOOD 



nitrogen content. This is most important to the vegetarian 
and to institutions where economy must be practiced. The fol- 
lowing variations in the composition of leading cereals will 
illustrate : 



Oats, maximum 

Oats, minimum 

Oats, American hulled . . 

Corn, maximum 

Corn, minimum 



Water. 


Nitro- 
genous 
substance. 


Crude 
fat. 


Carbo- 
hydrates. 


Fibre. 


20.80 


18.84 


IO.65 


64.63 


20.08 


6. 21 


6.00 


2. 11 


48.69 


4-45 


12. II 


13-57 


7.68 


63-37 


I.30 


22. 20 


1431 


8.87 


52.08 


7.71 


4.68 


5-55 


i-73 


72.75 


O.99 



Ash. 



8.64 

i-34 
2.03 

3-93 

0.82 



One sample of wheat flour may contain 14 per cent of nitro- 
genous substance, another may yield only 9. A day's ration, 
500 grams, will give 70 grams of gluten, etc., in the one case 
and only 45 in the other. This difference of 25 grams would be 
a serious factor in the dietary of an institution where little ad- 
ditional protein is given, and it alone might be the cause of 
dangerous under-nutrition. 

The next step would naturally be to determine how definitely 
these varying percentages mean varying nutrition. To this end 
a study of vegetable nitrogenous products in their combination 
or contact with cellulose, starch, and mineral matter is needed. 
Much work remains to be done before these questions can be 
even approximately answered. 

At the low cost of one cent a pound, common vegetables 
yield only about one-fifth as much nutriment as one cent's 
worth of flour, yet they contain essential elements and deserve 
to be carefully studied. 

The sanitary aspect of food demands a study of normal food 
and food value even more than of adulterants or of poisonous 
food, ptomaines and toxines. The cultivation of intelligent 
public opinion is most important, and each student should go 
out from a sanitary laboratory a missionary to his fellow men. 
That is, the office of a laboratory of sanitary chemistry should 
be so to diffuse knowledge as to make it impossible for educated 



THREE ESSENTIALS OF HUMAN EXISTENCE 7 

people to be deluded by the representations of unprincipled 
dealers. Freedom from superstition is just as important in 
this as in the domain of astronomy or physics. So long as 
chemists are employed by manufacturing concerns in making 
adulterated and fraudulent foodstuffs, so long must other 
chemists be employed in protecting the people until the public 
in general becomes wiser. A part of the common knowledge of 
the race should be the essentials of healthful living, in order that 
the full measure of human progress may be enjoyed. 

There is needed a greater respect for food and its functions 
in the human body, a better knowledge of its effect on the 
daily output of energy, its absolute relations to health and life, 
and the enjoyment of the same. The familiarity with these 
facts which is given by a few hours' work in the laboratory will 
make a lasting impression and will enable the student to benefit 
his whole life, even if he never uses it professionally. It is 
purely scientific knowledge, just as much as that derived from a 
study of the phases of the moon or the formulae of integration. 

The variety of operations in such work, calling for great 
diversity of apparatus and methods, is an educational factor 
not to be overlooked in laboratory training. 

For all detailed discussions and methods the reader is re- 
ferred to such works as those of Wiley, Allen, Leach, etc., but 
for the student who needs to study, as a part of general educa- 
tion, only typical substances, and such methods as can be 
carried out within the limits of laboratory exercises in a col- 
lege curriculum, the following pages are written. Not enough 
is given to frighten or discourage the student, but enough, it 
is hoped, to arouse an interest which will impel him at every 
subsequent opportunity to seek for more and wider knowledge. 

Food is too generally regarded as a private, individual matter 
rather than as a branch of social economy; it is, however, too 
fundamental to the welfare of the race to be neglected. Society, 
in order to protect itself, must take cognizance of the questions 
relative to food and nutrition. 

Formerly each race adapted itself to its environment and 



8 AIR, WATER, AND FOOD 

trained its digestion in accordance with the available food 
supply. In America to-day the question is not how to get 
food enough, but how to choose from the bewildering variety 
offered that which shall best promote the health and develop 
the powers of the human being, and, what is of equal impor- 
tance, how to avoid over-indulgence, which weakens the moral 
fibre and lessens mental and physical efficiency. In spite of all 
preaching, few really believe that plain living goes with high 
thinking. Professor Patten says that the ideal of health is to 
obtain complete nutrition. Over-nutrition as well as under- 
nutrition weakens the body and subjects it to evils that make 
it incapable of survival. 

No other form of social service will give so full a return for 
effort expended as the help given toward better diet for children 
and students. Fortunately help is coming fast. The United 
States Government is giving much study to food problems, and 
by publications is making available the work of other countries. 
The later bulletins listed in the bibliography at the end of this 
volume are especially valuable. What is now needed is a gen- 
eral recognition of the importance of the subject. 



CHAPTER II 

AIR AND HEALTH 

The air we breathe is a mixture of various gaseous substances 
containing more or less finely divided solid particles. What 
may be called "pure" air contains 20.938 per cent * by volume 
of oxygen, 0.031 per cent of carbon dioxide, 78.09 per cent of 
nitrogen, 0.94 per cent of argon and other rare gases belonging 
to the argon group. 

All the air with which we actually have to deal contains also 
varying amounts of moisture, expressed in terms of "relative 
humidity." Air at a low temperature can hold much less 
moisture than at a high temperature. For example, one cubic 
foot of air at 20 F. will hold 1.235 grains of water vapor, while 
at 70 7.98 grains will be held. The relative humidity is the 
ratio of the amount of moisture which the air actually contains 
to the amount which it could hold at the same temperature if 
completely saturated. As water vapor is lighter than dry air, 
the higher the humidity the less will a given volume of air 
weigh. This effect is familiar in the action of a barometer 
which falls on the approach of a rain storm, — the reading 
on such an instrument being dependent on the weight of air 
above it. 

Besides moisture, the air in cities may contain a variety of 
substances such as ammonia, sulphur dioxide, sulphur trioxide, 
etc., and almost always dust, bacteria, yeasts, and molds. 
Samples of air f taken in the down town districts of New York 
and Boston showed at the street level numbers of dust particles 
per cubic foot of air varying from 170,000 to 500,000, the num- 

* Benedict, Composition of the Atmosphere. Carnegie Institution, Publication 
No. 166. 

t G. C. Whipple and M. C. Whipple, Am. J. Pub. Health, 1913, 3, p. 1140. 

9 



IO AIR, WATER, AND FOOD 

ber gradually decreasing as the height above the street increased, 
until only about 27,000 were found in the air taken from the 
fifty-seventh floor of the Woolworth Building, 716 feet high. In 
a house, school room or public building the numbers of dust 
particles are equally variable, with a tendency to be somewhat 
higher, depending on the location of the building, and whether 
or not the air entering is purified. Thus in an investigation of 
the air of school rooms,* few cases were found where the num- 
bers were less than 200,000 per cubic foot, and they varied from 
this to over 1,500,000, the greater proportion being between 
200,000 and 600,000, much higher than is generally found in 
outdoor air. The numbers of bacteria found in the air are small 
compared to the dust particles, there being about 200" as many 
in outdoor air, and even less in indoor air, in 85 per cent of the 
samples taken in school rooms f the number of micro-organisms 
being less than 150 per cubic foot. In country districts the 
numbers of both dust particles and bacteria in the air are ex- 
tremely small. 

Under ordinary conditions the presence of dust and bacteria 
has no particular significance. In fact it is the opinion of most 
sanitarians that the danger of the spread of disease by the 
carrying of bacteria through the air is small, the contact neces- 
sary for this to happen being much closer than generally exists 
in offices and schoolrooms. There are certain special cases 
where dust particles may be harmful, — such as the dust con- 
sisting of small particles of metal found in certain factories, 
and the organic dust found in the air in certain rooms in textile 
mills. Some of these dusts, such as white lead, are themselves 
actually poisonous to the system, while others lodge in the 
lungs and lower the vitality so that pneumonia and tuberculosis 
are more liable to gain a footing. 

Poisonous gases are occasionally found in air, — the most 
important being carbon monoxide which comes from leaky gas 
jets or pipes, or from a defective furnace. As this gas has al- 

* Winslow, Am. J. Pub. Health, 1913, 3, p. 1158. 
f Winslow, loc. cit. 



AIR AND HEALTH II 

most no odor, insensibility may occur without the victim realiz- 
ing what is taking place. For this reason it has been found 
necessary, where this gas is used for lighting, to require the in- 
troduction into it of some substances with strong odors. Car- 
bon monoxide acts as a poison by combining with the haemo- 
globin of the blood, and preventing the absorption of oxygen. 

In the air of mines, methane, — or fire damp as it is called, — 
is sometimes present. This forms an explosive mixture with 
oxygen, and is frequently the cause of mine explosions. 

Respiration. — External respiration consists of alternately 
rilling and emptying the lungs. In the lungs, oxygen, breathed 
in with the air, is exchanged for carbon dioxide brought to the 
lungs by the blood. The blood leaving the lungs contains oxy- 
gen which is carried to all parts of the body, and passes * from 
the blood in the capillaries into the tissues where oxidation takes 
place. The carbon dioxide formed passes back into the blood 
and hence into the lungs. Expired air, therefore, contains less 
oxygen and more carbon dioxide than inspired air. An average 
composition would be, — oxygen, 16.03 P er cent; carbon di- 
oxide, 4.38 per cent; nitrogen, etc., 79 per cent. 

The process of exchange of oxygen and carbon dioxide in the 
lungs is partly a physicalone, — that is, the vapor pressure of 
oxygen is greater in the lungs than in the blood, and, therefore, 
oxygen passes from the former to the latter. With carbon 
dioxide the reverse is true. Therefore, if air high in carbon 
dioxide is breathed into the lungs this will increase the vapor- 
pressure of this substance, and hinder the ehmination of it from 
the blood. But it appears to be impossible to account for the 
interchange of gases on a purely physical basis, and, therefore, 
it is thought that enzymes, which aid in the interchange, are at 
work. 

Comfort. — The first two theories that were advanced to 

account for effects of discomfort when a room becomes " close" 

were based on the supposition that the products of respiration 

were poisonous w r hen taken back into the lungs. In one theory 

* See Hammarsten-Mandel. "A Text-book of Physiological Chemistry." 



12 AIR, WATER, AND FOOD 

this poisonous substance was supposed to be carbon dioxide. 
That animals cannot live in an atmosphere composed of nitro- 
gen and carbon dioxide, and that oxygen is necessary has long 
been known, but it was thought that carbon dioxide had a 
specific poisonous action and, therefore, should be present in any 
air used for human beings, in only very small amounts. This 
theory has been entirely disproved and carbon dioxide can no 
longer be regarded as in itself poisonous. If too much of the 
oxygen in the air becomes displaced by carbon dioxide it is im- 
possible for animals to utilize the oxygen left, but this only 
happens when the oxygen content decreases to about 12 per 
cent. Practically such a low per cent is never found, as inter- 
change of the air between a room and the outside is continually 
going on around windows and through walls. If, however, the 
oxygen is allowed to remain at about 21 per cent, very large 
quantities of carbon dioxide may be present without any ill 
effects. Experiments have shown conclusively * that carbon 
dioxide cannot be blamed for discomfort in a crowded hall or 
theatre. 

The other theory, — known as the " crowd poison" theory 
was based on some experiments which seemed to show that 
organic poisons were given off during respiration, and that these 
substances were the cause of the headaches and nausea some- 
times experienced by sensitive persons in " close" rooms. At 
the present time there are some adherents to this theory, but 
there has been little real evidence produced in its support. The 
first proofs of the non-poisonous character of exhalations were 
obtained by Formanek in a long series of experiments f and 
more recently Winslow J using the principles of anaphylaxis 
failed to obtain any results which showed the presence of the 
poisons (or toxins) in expired air. 

At the present time it is quite generally believed that sen- 

* See Crowder. "Ventilation of Sleeping Cars." Arch. Intern. Med., 191 1, 7, 

PP. 85-133- 

f Archiv fiir Hygiene, 1900, 38, p. 1. 
{ Loc. cit. 



AIR AND HEALTH 13 

sations of comfort and discomfort are dependent upon the rate 
of loss of heat from the body. If this is normal, then comfort 
results, if either too high or too low, then discomfort, headaches 
and nausea may follow. Just what this heat loss should be, 
measured in any system of units, is not known, but certain of 
the methods by which the loss takes place, and the factors 
which influence the rate may be discussed. 

There are three ways by which heat can be transferred from 
the body to the surrounding atmosphere. (1) Evaporation. — 
The change from the liquid to the gaseous state is accompanied 
by an absorption of heat. Thus when water evaporates from 
the surface of the body, heat is removed with it. (2) Trans- 
mission (by conduction and convection). Heat passes from a 
warm to a cold body when the two are in contact. For the 
greater part of the year the animal body is warmer than the 
atmosphere, and, therefore, the latter is continually receiving 
heat from the body. Since warm air rises, convection currents 
may be set up carrying away the heat already given up to the 
air. (3) Radiation. — The first two methods depend directly 
on the presence of matter. In radiation heat is transferred in 
all directions by means of ether waves, and the medium through 
which the radiation takes place does not necessarily become 
heated. There is no data available on the loss of heat from the 
body in this way, and we do not know what part it actually 
plays in comfort. 

These three methods by which heat may be given off from 
the body may be acting simultaneously, — in fact they generally 
are doing so, — and one or more may be negative in its action, — 
that is may be supplying heat to the body. Further, while they 
act entirely independently of each other, they are each in- 
fluenced by the same conditions of the atmosphere, and it is 
these physical conditions which are the ones capable of regu- 
lation, and which determine good or bad ventilation. These 
are, — temperature, humidity and motion. 

Temperature. — Temperature affects evaporation, because the 
higher the temperature of the air the more moisture is it capable 



14 AIR, WATER, AND FOOD 

of taking up. It affects conduction, because the greater 
the difference of temperature between two bodies the greater the 
amount of heat passing from that at the higher to that at the 
lower temperature. It affects convection, because convection 
currents are started by warm air rising and cooler air taking its 
place. 

Humidity. — Heat loss by evaporation is more dependent on 
humidity than on any other factor. Relative humidity is a 
measure of the per cent saturation of the air by water vapor, 
and it is obvious that the higher the humidity the less will be 
the opportunity for the air to take up more moisture, and, 
therefore, the less rapid the evaporation from the body. Trans- 
mission of heat from the body is affected by the humidity, be- 
cause moist air is a better conductor than dry air, and, therefore, 
the higher the humidity the greater the rate of heat conduction. 
(Relative humidity, as can be seen from a foregoing discussion, 
is itself affected by the temperature.) 

Motion. — The motion of the air influences evaporation by 
carrying away from the body more or less rapidly the air which 
has become completely saturated with moisture, and thus al- 
lowing access to unsaturated air. If the air and the body are 
perfectly quiet evaporation will be gradually retarded until it 
is nearly zero. Convection currents are movements in the air 
started by differences in temperature. These movements will 
be greatly increased by any motion in the air, and, therefore, 
the greater the motion the more rapid will be the transference 
of heat in this way. 

It is important to remember that these three factors, tem- 
perature, humidity and motion, — are always acting simul- 
taneously, and that there may be an increase in the rate of heat 
loss above the normal by one or more of them at the same time 
that the rest tend to decrease this rate. Furthermore, the same 
factor, humidity for example, may tend to increase the heat loss 
above the normal by one method, — perhaps by evaporation, — 
while at the same time, the same degree of humidity may tend 
to decrease below the normal the heat loss by another method, 



AIR AND HEALTH 15 

perhaps by transmission. The degree of comfort felt under any 
specified conditions is, therefore, the resultant of all effects, some 
tending to increase and others to decrease the rate of heat loss 
from the normal. 

This can be readily illustrated. Suppose that the temper- 
ature is 95 F., the humidity 90 per cent and there is but very 
little motion in the air. The result is well known, — a feeling 
of heaviness and considerable discomfort. Why? 

(1) The high temperature allows the air to take up a con- 
siderable amount of moisture, thus tending to increase the heat 
loss by evaporation, with the consequent cooling effect on the 
body. On the other hand, the heat loss by conduction, con- 
vection and radiation are only very small as they depend on 
the difference of temperature of the body and the air. 

(2) The high humidity prevents the rapid evaporation of 
moisture, and, therefore, tends to decrease the heat loss from the 
body. This more than counteracts the increased capacity of 
the air for moisture, due to the high temperature. On the 
other hand, the high humidity makes the air a better conductor 
of heat, and, therefore, tends to increase the heat loss by con- 
duction. This, again, is counteracted by the high temperature, 
temperature being the more important factor in this method of 
loss. 

(3) The very slight motion of the air tends to decrease the 
heat loss by evaporation and convection. 

The net result is that heat does not leave the body as rapidly 
as it should, and we feel hot and uncomfortable. 

Application of this theory of regulation of loss of heat is not 
wholly adequate to explain all conditions. Another factor seems 
to be involved, that of loss of moisture, apart from any loss of 
heat which accompanies this. "Probably much of the harm 
attributed to damp and to cold is due to diminished water cir- 
culation, etc."* With this added factor it is possible to ex- 
plain most of the uncomfortable conditions. The uncertainty 
of the theory lies m the fact that we have been unable to test it 

* Macfie, Air and Health. 



i6 



AIR, WATER, AND FOOD 



THE CURVE OF COMFORT 






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Mean annual temperature and humidity of health resorts: 



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rabl 


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Alexandria 6 
Cairo 7 
Bermuda 8 

e to white man's residence: 


Arequipa 
Luxor-winter 
Los Angeles 
Madeira 


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IO 

ii 


New Orleans 12 
Havana 13 
Malay Archipelago 14 


Persia 
India 
Singapore 



A-B Most comfortable for indoor workers (Hill). 



AIR AND HEALTH 1 7 

experimentally and to determine the exact heat loss due to each 
factor. 

Hill * has plotted a series of curves which are intended to 
represent the various conditions of comfort in terms of tem- 
perature and humidity. Thus it is seen that a temperature of 
55 F. and a humidity of 70 per cent gives comfort, and as the 
temperature increases the humidity must be decreased. At 
68° F., the temperature generally desired in the house, the 
humidity must be around 50 per cent. 

Ventilation. — In ventilating a public building or a house, it 
is necessary to supply a sufficient quantity of air in the proper 
condition. In most cases this condition is, that the air in the 
room shall be at a temperature of 68° to 70 F., and with a 
humidity of 50 to 70 per cent. As long as the humidity does 
not go too high, it seems to be a secondary factor so far as health 
is concerned. More discomfort is felt from overheating than 
from any other cause. This is also true in many factories, but 
there are some where high humidity must be considered, such 
as is necessary to maintain in connection with certain textile 
operations. It should be remembered that the higher the tem- 
perature the more sensitive does one become to high humidity. 

Another condition which must be met in ventilation practice 
is that governed by the carbon dioxide content of the air. As 
pointed out above, this substance is not itself poisonous, but it 
is useful in serving as an index of the amount of unused air be- 
ing supplied. The normal individual gives off from 0.6 to 0.8 
cubic feet of carbon dioxide per hour, and this will gradually 
accumulate in a room unless the air is continually being replaced. 
The amount of carbon dioxide present in a room can, therefore, 
be used to determine whether or not there is sufficient replace- 
ment of used air by fresh air. The allowable amount of carbon 
dioxide is about 10 parts per 10,000 of air. Amounts above this 
may be allowed in certain special cases where the carbon dioxide 
does not come from man or animals. If only 6 or 7 parts are 
present, the ventilation may be considered excellent. In order 

* Hill, Recent Advances in Physiology and Biochemistry. 



l8 AIR, WATER, AND FOOD 

to accomplish this about 2000 cubic feet of fresh air per person 
per hour must be supplied. The amounts actually recommended 
depend somewhat on the use to which the room or building is 
to be put, these amounts varying between 1000 cu. ft. for a 
waiting room and 2500 for a hospital. Where it is difficult to 
determine how many people will be present the calculations may 
be based on the number of complete changes of air per hour, 
these being from one to five in a residence, and from one to two 
in an auditorium.* 

It is also possible to calculate from analytical data the inter- 
change of air going on under given conditions, and thus test the 
efficiency of a ventilating system. If, after a room has been 
occupied and the occupants removed, the air is analyzed for 
carbon dioxide, the room allowed to remain a definite length of 
time, and another analysis made, the interchange may be cal- 
culated from a formula given by Barker: f 



v =Wfc-:) 



where C is the contents of the room in cubic feet, T the time in 
hours between the original amount of carbon dioxide ki in one 
cubic foot of air, and the final amount k 2 in one cubic foot of 
air, a the proportion of carbon dioxide in one cubic foot of pure 
atmospheric air, and V the interchange in cubic feet per hour. 

Ventilation depends on the movement of air currents in such 
a way as to continually supply fresh air and to remove used 
air. This must be done so that no drafts will be felt at any 
part of the room. The system actually used will depend on 
the kind of building and room, — as well as on the kind of heat- 
ing used. In the ordinary dwelling house ventilation is almost 
always left to look after itself. Even in the best built houses 
there is going on constantly an interchange of air around the 
windows and doors. This is not sufficient on winter evenings 

* Greene, "Elements of Heating and Ventilation," p. 23. 
f Baker, "The Theory and Practice of Heating and Ventilation," p. 164. A 
number of other useful ventilating formulae are also given. 



AIR AND HEALTH 



19 



when kerosene or gas lamps are burning, and most rooms soon 
become stuffy. To aid this natural ventilation, windows, open 
fire places and hot air furnaces are used. Excellent results may 
be obtained from the careful use of the open window, but it re- 
quires considerable time as well as care to operate them so that 
no drafts will result. Where a hot air system of heating is used 
a house may be well ventilated, — the air which is forced in 
through registers going out after proper circulation, through ven- 
tilators or around windows. Care should be taken to place 
registers to get this circulation. 

In a large building, — office, educational, or auditorium, — the 
problem is somewhat different. Here it is useless to depend on 
natural ventilation and some artificial means must be employed. 
There are two general methods of air circulation in use, upward 
and downward. Both have their advantages and disadvantages. 
Upward ventilation would seem theoretically the best, as ex- 
pired air, being warm, rises and creates an upward current, 
which can be easily drawn into an outlet. This system can be 
used, but it presents certain difficulties. The first is that un- 
less air comes into the room through a very large number of 
small holes in the floor, drafts of cold air around the feet are 
certain to be felt. This would only be practical in an audi- 
torium with stationary seats. Besides, objection is sometimes 
made that odors from the clothing are made more noticeable by 
being carried past the nose. The reverse system, downward ven- 
tilation, seems to be more practical. Here the air is introduced 
from the ceiling and is drawn out through ducts in or near the 
floor. More often air is introduced from the walls of the room. 
In this case it is necessary to so arrange the inlet and outlet 
that air from the former will circulate around the room before 
reaching the latter. To do this, the outlet is generally placed 
a little below the inlet on the same wall, this being on the cold 
side of the room. The air may be forced into the room under 
pressure from a fan, called the plenum system, or may be drawn 
out from the room by a fan in the outlet, called the vacuum 
system. 



20 AIR, WATER, AND FOOD 

In cities where there is necessarily much smoke and dirt, 
it may be considered best to purify, in some way, the air 
entering a building. The simplest method is to screen the in- 
coming air through fine wire gauze or cheese cloth. A more 
effective way is by means of air washers. All of these, and 
there are a number of them on the market, depend on the pas- 
sage of the air through a spray of water which removes dirt, 
bacteria and soluble substances. Since these machines spray 
water into the air they are also humidifiers, and may be used as 
such, particularly in textile factories where it is necessary to 
carry on certain operations in moist air. 

It is also possible to take air out of a room, wash it, cool it 
and send it back into the same room.* This would effect a 
saving of coal if it were practical to operate. 

Another method which has been in some use for purifying air 
is by means of ozone. During the last year there has been much 
discussion on this subject,! and very serious doubts have been 
thrown on the real usefulness of this method. That ozone in 
the presence of a large amount of moisture is a good disinfectant 
cannot be denied, but under the dry conditions of the atmos- 
phere its germicidal effect is small. However, in most cases it 
is not bacteria which we need to kill, but odors. On this point 
the evidence is not quite so clear. Most are agreed that the 
odors disappear, but it is still a question whether the substances 
producing them are actually destroyed, or whether the odors 
are masked by those of ozone. From a standpoint of health, 
this would also be immaterial if it could be proved that the 
ozone itself was harmless to breathe. At the present time the 
evidence seems to be the other way. 

* See article on Recirculated Air. McCurdy, Am. Phys. Ed. Rev., Dec, 1913. 
f Jordan and Carlson, /. Am. Med. Assn., 1913, 61, pp. 1007-1012; Norton, 
Eng. Rec, 1913, 68, p. 732; Vosmaer, /. hid. Eng. Chem., 1914, 6, p. 229. 



CHAPTER III 
air: analytical methods 

In an investigation of the air of any room or public building 
it is not enough to make one or two observations, as these might 
be entirely misleading, but a sufficient number must be taken 
to get a fair estimate of the conditions. Thus in a room, read- 
ings of the physical instruments must be made and samples 
for chemical analysis taken at a number of points, and these 
repeated at intervals of five or 10 minutes until six or eight have 
been taken. Slight changes constantly occur which are not of 
any importance in practical work, but fortunately most of the 
instruments and most of the methods used are not delicate 
enough to be influenced by changes of this character. In short, 
it is average conditions which are of importance, and which 
should be recorded. 

Physical Determinations. — Temperature. — The use of the 
thermometer is too well known to need any detailed statement. 
Mercurial thermometers are the most accurate for practical 
work, but care should be taken that the bulb of the thermome- 
ter is suspended in the air and not placed against a wooden 
back, as in the latter case the reading lags behind the actual 
changes in the temperature of the air. Where it is desired to 
have a continuous record, recording thermometers are to be 
recommended. These depend on the contraction and expan- 
sion of a metal combination, with the changes of temperature, 
the metal being connected with a pen which records the changes 
on a paper disc moved by clockwork. 

Pressure. — Air pressure is measured by barometers, of which 
there are two types, — mercurial and anaeroid, both of which 
are well known. Since the barometric reading depends on the 
weight of the column of air above the instrument, the reading 



22 AIR, WATER, AND FOOD 

will vary with the distance above sea level, and with the com- 
position of the air. In the latter case the only important factor 
is moisture. As water vapor is lighter than dry air, the larger 
the moisture content the lighter the moist air and the less the 
pressure. Thus a low barometric reading indicates the ap- 
proach of a storm. 

Humidity. — Relative humidity has already been described. 
The most accurate method of measurement is by means of wet 
and dry bulb thermometers. The rate of evaporation of water 
into air at any one temperature depends on the amount of 
moisture already present. Since evaporation is accompanied by 
absorption of heat, the surface from which the water evaporates 
will be cooled in proportion to the rate of evaporation. If the 
bulb of a thermometer is surrounded by a film of moisture, 
which can readily be done by means of a piece of cloth or wick 
with one end dipped in a reservoir of water, this cooling can be 
measured by the lowering of the temperature below that of a 
thermometer whose bulb is surrounded by air alone, and the 
lowering is proportional to the relative humidity. In the ap- 
pendix will be found a table from which the relative humidity 
can be obtained from the reading of the dry and wet bulb ther- 
mometers. In order that the wet bulb thermometer may come 
quickly to equilibrium an instrument called the psychrometer 
has been devised for rapidly rotating the thermometers. 

Another method of measuring the humidity is by means of 
the hair hygrometer. In this instrument a number of horse 
hairs are placed under tension by means of a small weight. 
The distance to which the hairs will be stretched will depend on 
the amount of moisture taken up from the air, — the higher 
the moisture the greater the stretching. The weight can be 
readily connected to an indicator which will record the rela- 
tive humidity on a dial, or a pen can be attached, to make a 
recording instrument, in a similar manner to that used with a 
recording thermometer. 

Motion. — Where the velocity of air is considerable, as in the 
case of wind or in such places as ventilation ducts, measure- 



AIR: ANALYTICAL METHODS 23 

ments can be made by the use of anemometers. However, in a 
room, the movement of air is much too slow, and the direction 
of currents too varied, for such an instrument to be of use. 
The best method is by use of smoke from a joss stick or cigar.* 

Dust. — The simplest method for determining dust in air is to 
draw a measured quantity of air through a weighed tube con- 
taining a cotton plug. For this it is necessary to have a suction 
pump, — the variety which may be attached to a water faucet 
is useful, — a meter, such as a gas meter, and a tube containing 
a cotton plug. The tube with the plug should be dried in a 
desiccator before each weighing as moisture may be absorbed 
from the air passed through. Knowing the amount of air and 
the increase of weight of the cotton filter, the amount of dust 
per unit volume of air can be calculated. Where the amount of 
dust is large, the cotton plug can be replaced by one of granulated 
sugar. The amount of dust is then determined by dissolving 
the sugar in water and then filtering through a weighed Gooch 
crucible. 

The most accurate determinations of dust particles can be 
made by means of the "Dust Counter" or the "Koniscope." 
Both of these instruments f are too expensive to be very generally 
used. 

An apparatus for taking dust samples of air has recently been 
described by Baskerville,{ and would seem to be useful and 
sufficiently accurate for practical purposes. 

Chemical Determinations. — The first systematic study of 
the atmosphere was made by Scheele, in 1779, shortly after the 
discovery of oxygen. Since that time more and more accurate 
methods have gradually been developed, culminating in that 
used recently by Benedict. § 

* Shaw, " Air Currents and the Laws of Ventilation." Cambridge, 1907. 

t See "Standard Methods for the Bacterial Examination of Air," Am. Pub. 
Health Assn., 1910, p. 38. 

X J. Ind. Eng. Chem., 1914, 6, p. 238. 

§ For a detailed history of air analysis see Benedict, "The Composition of the 
Atmosphere with Special Reference to its Oxygen Content," Carnegie Institution 
of Washington, 191 2, Publication No. 166. 



24 AIR, WATER, AND FOOD 

In practice the only chemical test made on air is that for 
carbon dioxide. In cases of poisoning, tests may be made for 
carbon monoxide or methane, and in experiments with respira- 
tion, oxygen determinations together with those for carbon 
dioxide are considered necessary. 

The methods for the determination of carbon dioxide are all 
based on absorption by alkalies, the amount of this absorption 
being measured either by direct determination of the diminution 
of a given volume of air, or by determination of the amount of 
alkali used for the absorption. 

Collection of Samples. — Methods for collecting samples of air 
for chemical analysis will vary somewhat with the method and 
apparatus used. In certain cases the sample is measured 
directly into the analytical apparatus, while in others, — and 
these are the more practical methods, — the sample is first col- 
lected in a balloon or bottle. Where large amounts are needed, 
as in the Pettenkofer method, the samples are collected in a 
four- or six-liter bottle, the volume of which has been determined 
by weighing both empty and filled with water. The bottle is 
fitted with a two-hole rubber stopper with a short piece of glass 
tubing to serve as an inlet in one hole and a long brass tube ex- 
tending to the bottom of the bottle, in the other hole. This 
brass tube is connected to a bellows with the valves arranged so 
that air will be drawn out of the bottle. Pumping should be 
continued until the air originally in the bottle has been entirely 
replaced, which will take from 30 to 50 strokes of the bellows. 
The stopper and tube are then removed, and the bottle closed 
with a stopper as described on page 34. 

For the Walker and the Cohen and Appleyard methods a 
much smaller volume is all that is needed, — from 500 c.c. to 
two liters. The simplest method is to fill the bottle with water 
and pour it out. This has the disadvantage that expired air 
from the collector may reach the bottle. 

A better method is to fit two bottles each with a 2-hole 
rubber stopper. In one hole of the stopper of bottle (A) (Fig. 1) 
insert a short piece of glass tubing, and in the other a longer 



AIR: ANALYTICAL METHODS 



25 



piece of tubing extending nearly to the bottom of the bottle. 
In the stopper of (B) insert a short piece of glass tubing just 
reaching through the stopper, and a longer tube extending 
nearly to the bottom, and 
fitted with a piece of small 
bore rubber tubing and a 
pinch clamp. Connect the 
short tube of bottle (B) with 
the long tube of (A) by means 
of a rubber tube and close 
with a pinch clamp. Fill (B) 
with recently boiled water, 
open clamp (a), close clamp 
(b) and insert stopper with 
connections, into the bottle. 
Then close (a). Invert (B) 
at the point at which the sam- 
ple is to be taken. Release 
the pinch clamp (a) , and then 
open the clamp (b) . The bot- . 
tie filled with air (B) is then 
closed with a solid rubber 
stopper and is ready for 
analysis. If bottle (A) is 
larger than (B) it can be 
used, together with the water, for taking a number of samples 
of air. 

Another method by which sampling is made easier, but which 
does not give such accurate results, is the steam vacuum method. 
The apparatus is set up as in Fig. 2. Steam is supplied from a 
two-quart oil can nearly filled with water, or if preferred, from a 
liter flask. A rubber tube and piece of glass tubing connects 
the steam can with the inverted bottle, the size of which de- 
pends on the method of analysis used, the tube extending to 
within an inch of the bottom of the bottle. The bottles are 
made for ground glass stoppers, but are fitted with rubber 




Fig. i. 



26 



AIR, WATER, AND FOOD 



stoppers to which have been applied a thin coating of vaseline. 
Too much vaseline should be avoided, as it prevents the stopper 
staying in after the sample has been collected. The rubber 
stoppers should be one size larger than would ordinarily be used. 
To prepare the bottle, fill the can two-thirds full with water, 
and boil for a few minutes to expel carbon dioxide and air. In- 




FlG. 2. 

vert the empty bottle over the end of the tube, and allow to 
remain for three minutes. Keeping the bottle inverted, re- 
move it from the, tube, and quickly insert the rubber stopper. 
The stopper may be pushed in more securely by holding it 
against the table with a slight pressure, and keeping it there 
until the vacuum starts to form. When cool, the stopper should 



AIR: ANALYTICAL METHODS 27 

project at least one-half an inch in order to be easily removed. 
A number of bottles can be prepared in the laboratory, and quite 
easily transported. All rubber stoppers which are used should 
first be boiled in dilute caustic soda, then in a dilute solution of 
potassium bichromate and sulphuric acid and thoroughly 
rinsed. 

To collect the sample it is necessary only to remove the stopper, 
taking care to hold the bottle away from the face in order to 
prevent contamination from the carbon dioxide of the breath. 

At the time of collecting the samples the following observations 
should be recorded: room, date, time, weather, place in room, 
number of people present, number of gas jets or lamps burning, 
number of doors, windows and transoms, methods of heating 
and ventilation, and anything else which would tend to in- 
fluence the amount of carbon dioxide present. 

•In collecting samples, care must be taken to avoid currents of 
air or the close proximity of people. Exact duplicate analyses 
can be obtained only in empty or in nearly empty rooms. Even 
two sides of the same room will probably show differences, but 
two samples taken carefully side by side ought to agree within 
0.05 part per 10,000. 

Carbon Dioxide. — The most accurate analyses of air have 
been those obtained by Benedict by means of an apparatus 
especially designed by Dr. Klas Sonden* The analysis de- 
pends upon the measurement of the decrease in volume of a 
sample of air after contact with a caustic alkali solution. An- 
other accurate apparatus on the same principle is that of Petter- 
sen-Palmquist, f which has been modified by Rogers, { and 
more recently by Anderson. § In all of these forms the manipu- 
lation is rather delicate, the apparatus is bulky to transport, 
and when obtained, the results are much more accurate than is 
necessary for any practical work. 

* A description of this will be found in Publication No. 166, Carnegie Insti- 
tution of Washington, already referred to. 

f For description see Rosenau, " Hygiene and Preventive Medicine." 
t See catalogue of Eimer and Amend. 
§ /. Am. CJiem. Soc, 1913, 35, p. 162. 



28 AIR, WATER, AND FOOD 

Walker Method. — The method to be most recommended for 
practical analyses for carbon dioxide is that proposed by Walker* 
It has been carefully studied in this laboratory t and slightly 
modified. The results are accurate to tenths of a part per 10,000. 

Principle. — To a definite volume of air, usually one to two 
liters, is added a measured amount of standard barium hydrox- 
ide, care being taken to avoid contact of the solution with the 
air. After the absorption of the carbon dioxide, the solution is 
filtered under reduced pressure through asbestos and the clear 
barium hydroxide received into a known excess of standard 
hydrochloric acid. The absorption bottle is rinsed out with 
water free from carbon dioxide. The excess of acid is then 
determined by titration with barium hydroxide. It is essential 
for the complete absorption of the carbon dioxide that the barium 
hydroxide be largely in excess, so that not more than one-fifth 
of it is neutralized; furthermore, the absorbing solution must be 
shaken with the air for a considerable time. 

Reagents and Apparatus. — The standard solutions used are 
N/50 hydrochloric acid, and barium hydroxide, approximately 
N/100, its exact strength relative to the acid being found daily by 
titration. It will be found advantageous- to use solutions of 
this strength, somewhat more dilute than those recommended 
by Walker, on account of the increased accuracy with air nearly 
free from carbon dioxide. The decreased range of usefulness is 
readily compensated by the employment of smaller samples of 
the impure air. 

The barium hydroxide is preserved with especial care. The 
hard-glass bottle containing it, placed on a high shelf so that 
the measuring apparatus can be rilled directly by gravity, is 
heavily coated on the inside with barium carbonate. The bottle 
is closed by a rubber stopper with two holes, one of which car- 
ries the siphon tube dipping to the bottom of the bottle and 
supplying the measuring burette, while the other carries a fairly 
large glass T. (Fig. 3). 

* /. Chem. Soc, 1900, 77, p. 11 10. 

t Woodman, /. Am. Chem. Soc, 1903, 25, p. 150. 



AIR: ANALYTICAL METHODS 



20 



A 



*; 




From one-half the horizontal arm of this projects a glass tube 
carrying the device for protecting the solution. This device is 
shown drawn on a somewhat larger scale in the same sketch. 
The horizontal tube enters the T tube 
far enough to support the apparatus. 
Connection is made by a closely-fitting 
rubber tube. The longer tube, reach- 
ing nearly to the bottom of the test- 
tube, carries a fairly good-sized cal- 
cium-chloride tube which contains T 
soda-lime, enclosed in the usual man- 
ner by plugs of cotton. The test-tube 
contains five to 10 c.c. of dilute (about 
N/50) caustic potash colored with phe- 
nolphthalein, the whole serving to in- 
dicate the efficiency of the soda-lime. 
From the other end of the horizontal 
arm of the T projects, in the same way, a long tube bent at 
right angles fitting by a rubber stopper into the top of the 
burette, thus making the whole a closed system, much after 
the manner of Blochmann* Any air entering the bottle when 
the solution is drawn from the burette or when the burette 
is filled again must have come through the protecting appa- 
ratus. This will be found efficient if care is taken in the selec- 
tion or preparation of the soda-lime.f 

The burette used for the barium hydroxide is a glass-stop- 
pered one, differing somewhat from the ordinary form. The 
portion below the graduations is narrowed and bent at a right 
angle. This horizontal part is fitted with an ordinary glass 
stop cock. This gives no trouble when kept well vaselined. 
The tip of the burette is kept covered with a little rubber cap 
when not in use, to prevent clogging from the formation of 
carbonate. The apparatus could easily be arranged with a 



Fig. 3. 



* Ann. Chem., (Liebig), 1887, 2 37» P- 39- 

t Directions for preparing a good quality of soda-lime are given by Benedict 
and Tower, /. Am. Chem. Soc, 1899, 21, p. 396. 



So 



AIR, WATER, AND FOOD 



special pipette for the delivery of a definite charge of a baryta 
solution. 

The apparatus used for filtering off the barium .carbonate is 
shown in Fig. 4. On the base of a ring stand is placed an ordi- 
nary filter bottle of about 250 c.c. capacity closed by a rubber 
stopper with one hole. The suction pump is connected with the 

tube on the side of the bottle. A Gooch 
filtering-funnel, the upper part of 
which is cut off so that the remainder 
above the constriction is about an 
inch long, is put through the rubber 
stopper. The tip projecting into the 
bottle is bent so that the liquid shall 
flow down the side and not spatter. 
A rather close coil of stout platinum 
wire placed above the narrow portion 
serves as a support for an asbestos 
filter. A two-cm. Gooch filter plate 
serves as well as the platinum wire. 
In the upper part of the tube is a 
tightly-fitting rubber stopper, through 
which passes a narrow glass tube 
extending to within one-eighth inch 
of the asbestos layer, and provided 
above the stopper with a stop cock. 
Connection is made with the short 
FlG - 4- tube of the inverted bottle by means 

of a rubber tube about 4 inches in length. 

The inverted bottle is a carefully calibrated one of about 
one liter capacity, and is used for collecting the sample, the 
method preferably being by water displacement as described 
on page 25. Record the temperature and barometric pressure 
at the time the sample is taken. After collecting the sample the 
bottle is closed by a solid rubber stopper. For filtering, this is 
replaced by a rubber stopper through which pass two glass 
tubes. The longer tube reaches nearly to the bottom of the 




AIR: ANALYTICAL METHODS 3 1 

bottle, is bent as shown, and contains a glass stop cock. The 
shorter tube ends internally just flush with the stopper, and out- 
side is fitted with a stop cock and projects just far enough to 
make connection with the rubber tubing. The glass stop cocks 
may be replaced by rubber tubing and Mohr pinch clamps. 

The filter is made of washed asbestos, free from acids, in the 
manner usual for Gooch crucibles. The same filter will do for 
a number of determinations. The asbestos layer should be 
about one-eighth of an inch thick and should be washed with 
distilled water. 

Procedure. — Remove the stopper from the calibrated bottle 
containing the sample of air, and run in rapidly from the burette 
about 25 c.c. of the barium hydroxide solution, the exact amount 
being determined from the burette readings. Immediately re- 
place the rubber stopper, place the bottle on its side and shake 
at very frequent intervals for 20 minutes, giving a sort of rotat- 
ing motion so that the solution will spread over the bottle, and 
thus expose a large surface for absorption of the carbon dioxide. 

While the absorption is going on prepare the filter (although 
it is better to prepare this, and to standardize the barium hydrox- 
ide before starting the determination) and also make about 
100 c.c. of wash water for each determination. This latter is 
done by adding to distilled water one c.c. of a 10 per cent 
barium chloride solution and three drops of phenolphthalein, 
then titrating with the barium hydroxide to a faint permanent 
pink. Keep in a stoppered flask until wanted. 

Standardize the barium hydroxide against the hydrochloric 
acid in the usual manner. Employ some wash water for 
diluting in place of distilled water, which contains some carbon 
dioxide. 

Measure into the filter bottle from a burette about 13 c.c. (or 
an amount slightly more than equivalent to the barium hydrox- 
ide used) of N/50 hydrochloric acid, the exact amount being 
obtained from the burette readings. 

After the absorption is finished remove the rubber stopper 
from the bottle, and wash the stopper with a little of the wash 



32 AIR, WATER, AND FOOD 

water, letting the washings run into the bottle. Insert the two- 
hole rubber stopper with connections for filtering and invert as 
shown in the figure. 

Open the upper stop cock and turn on the pump. Now slowly 
open the filter stop cock and control the flow of liquid entirely 
with this cock. The barium carbonate remains on the asbestos, 
and the clear baryta solution which passes through is at once 
neutralized by the hydrochloric acid. When all the liquid has 
passed through allow the pump to act for a few minutes until 
the bottle is partially exhausted, then close the filter cock. 

Pour some of the wash water into a small beaker, dip the end 
of the longer tube into it, and by opening the stop cock allow 
about 20 c.c. to flow into the bottle before closing it. Un- 
clamp the bottle and shake thoroughly while held horizontally 
and still attached to the filter. Clamp it in place again, turn on 
the pump, and draw the wash water through the filter. Repeat 
this twice. Generally at the third washing the wash water no 
longer turns pink, showing that the barium hydroxide has been 
completely removed. If the pink color persists wash again. 

Remove the filter bottle and titrate in the bottle, for the ex- 
cess of acid, with barium hydroxide. The end point is a distinct 
pink which is permanent for one minute. 

To obtain the amount of carbon dioxide subtract the number 
of cubic centimeters of N/50 acid used from the number of cubic 
centimeters of acid equivalent to the barium hydroxide used. 
This will give the amount of carbon dioxide in the sample in 
terms of N/50 acid, from which the actual number of grams of 
carbon dioxide can be obtained. From the table in the ap- 
pendix * obtain the weight of one cubic centimeter of carbon 
dioxide for the conditions of temperature and pressure observed 
when the sample was taken. From this the volume of carbon 
dioxide in the sample can be calculated, and knowing the vol- 
ume of the bottle, and making allowance for the 25 c.c. of alkali 

* Dietrich's Table, the one in general use, is not absolutely correct, the weight 
of a cubic centimeter of carbon dioxide at o° C. and 760 mm. being somewhat 
different from that given at present by the best authorities, but it is sufficiently 
close for any but the most exacting work. 



AIR: ANALYTICAL METHODS 33 

added, the parts of carbon dioxide per 10,000 of air can be 
calculated. 
A sample calculation follows: 

Standardization: — 1 c.c. Ba(OH) 2 = 0.48 c.c. N/50 HC1. . 
Volume of bottle = 991 c.c. Temperature = 18 C. Ba- 
rometer = 764 mm. 
Total Ba(OH) 2 used 58.02. HC1 used = 26.08. 
58.02 c.c. Ba(OH) 2 = 58.02 X 0.48 = 27.85 c.c. HC1. 
'27.85 — 26.08 = 1.77 c.c. N/50 acid equivalent to the C0 2 

present. 
Since 1 c.c. N/50 acid = 0.44 mg. C0 2 , then there are 

present in the sample 0.78 mg. C0 2 . 
1 c.c. C0 2 at 18 and 764 mm. weighs 1.817 mg. .*. 991 — 
25 = 966 c.c. of air contains .429 c.c. C0 2 or 4.4 pts. C0 2 
per 10,000. 
If the amount of carbon dioxide present exceeds 25 parts per 
10,000, either a 500 c.c. bottle may be used for collecting the 
samples, or double the quantities of barium hydroxide and hydro- 
chloric acid should be added. Such a condition rarely exists 
in practical work. 

Pettenkof er Method. — The method which for many years 
was generally employed for the estimation of carbon dioxide in 
the air of rooms is a modification of that originally devised by 
Pettenkofer.* While this method is convenient, and for a long 
time has been the favorite, it is now quite generally recognized 
that it contains inherent sources of error which can be obviated 
only by the use of complicated apparatus and extreme skill in 
manipulation. It should, therefore, be borne in mind that the 
results obtained are generally too high even though agreeing 
closely among themselves. 

Principle. — The principle is essentially the same as that of 
the Walker method, i.e., the absorption of carbon dioxide from 
a known volume of air in barium hydroxide solution and the 
titration of the excess with standard sulphuric acid. 

* Pettenkofer, Annalen, 2, Supp. Band, 1862, p. 1; Gill, Analyst, 1892, 17, 
p. 184. 



34 AIR, WATER, AND FOOD 

The samples are collected in four- or six-liter bottles, as de- 
scribed on page 24, each provided with a rubber stopper carry- 
ing a glass tube over which a rubber nipple or cap is slipped. 
Note particularly the temperature and barometric pressure. 

Reagents and Apparatus. — The solutions used are sulphuric 
acid of such a strength that one c.c. equals one milligram of 
carbon dioxide (see appendix B), and barium hydroxide solu- 
tion of approximately equal strength. Since it is impracticable 
to prepare exact solutions of barium hydroxide, and to keep 
them without change, the exact value of the barium hydroxide 
solution must be found by titration against the standard sul- 
phuric acid. This standardization, as well as the subsequent 
titration, is best made in a small flask to lessen the error from 
absorption of carbon dioxide from the air. It will be found 
most generally satisfactory to measure into the flask about 25 
c.c. of the barium hydroxide, add a drop of phenolphthalein 
solution, and titrate with the sulphuric acid to the disappear- 
ance of the pink color. In all cases the first end-point should 
be taken as the correct one, because the pink color will some- 
times return on standing. 

The apparatus consists of the collecting bottles, 50 c.c. bu- 
rettes, a stoppered bottle of hard glass of 40 c.c. capacity, and 
a 25 c.c. pipette. 

Procedure. — Remove the cap from the tube in the stopper 
of the bottle, insert the tip of the burette so that it projects into 
the bottle, and run in rapidly 50 c.c. of barium hydroxide from 
the burette. Replace the cap, place the bottle on its side and 
roll or shake it at frequent intervals for 45 minutes, taking care 
that the whole surface of the bottle is moistened with the solu- 
tion each time. At the end of this time thoroughly shake the 
bottle to mix the solution, remove the cap, and pour the solu- 
tion into a stoppered bottle of hard glass of 40 c.c. capacity, 
taking care that the solution shall come in contact with the air 
as little as possible. Under these conditions a full well-stoppered 
bottle may safely stand for days before titration. For the 
titration, measure out with a pipette 25 c.c. of the clear liquid 



AIR: ANALYTICAL METHODS 35 

into a 75 c.c. flask and titrate it with the sulphuric acid as in 
the standardization. 

The calculation is similar to that given under the Walker 
method except that it should be remembered that only one- 
half of the barium hydroxide was used in the titration. 

Rapid Methods. — In addition to the above methods for de- 
termining carbon dioxide just described, there are general tests 
which can often be used with advantage. If within the space 
of a few hours some 50 or more tests are to be made, and com- 
parative results rather than great accuracy are required, some 
simpler form of apparatus is desirable. 

Such an apparatus, to be satisfactory, should meet, so far as 
possible, the following requirements: 

(1) It should be sufficiently compact and portable to be car- 
ried in the hand from place to place. 

(2) It should be as simple in construction as possible, and its 
use should not involve delicate measurements. 

(3) If possible, the apparatus should be made entirely of glass, 
avoiding prolonged contact of corks or of rubber connectors 
with any dilute solution which may be used. 

(4) It should be so constructed as to protect the solution at 
all times from the carbon dioxide of the air, especially while the 
determination is being made, because of necessity such an ap- 
paratus must be used within the area of contamination. 

(5) The complete apparatus should be sufficient for 50 or 
more determinations. 

(6) It must be capable of giving results of a reasonable de- 
gree of accuracy, say within 0.5 part of carbon dioxide in 10,000 
parts of air, in the hands of persons having little or no chemical 
knowledge and minimum skill in manipulation. 

(7) If a solution be used in the apparatus it should be one 
which can be prepared easily from chemicals readily obtained; 
the solution must maintain its efficiency for a reasonable length 
of time, if protected from external influences; and the solution 
should be one that is not at all dangerous or obnoxious to use. 

Simplicity of apparatus is much to be desired, but it should 



36 



AIR, WATER, AND FOOD 



not be gained at too great sacrifice of accuracy. Even when no 
greater precision is required than is necessary to meet the de- 
mands of practical work, it is out of the question to measure the 
test solution by means of an ordinary pipette or to preserve it 
for any length of time in stoppered vials; the strength of the 
solution is almost certain to be reduced by contamination with 
the breath, or by contact with rubber or cork. 

It must ever be borne in mind that extreme care is necessary 
in the preparation and use of these very dilute solutions, the 
strict observance of conditions which might well be neglected 
in ordinary analytical procedures being here an essential factor 
of success. 

For the preservation and measuring of the test solution an 
apparatus has been devised which appears to answer the above 
requirements, and in actual practice has been found satisfactory.* 

The essential feature of this 
apparatus consists of an auto- 
matic pipette for measuring 
the test solution. This is a 
modified form of the pipette 
first proposed by G. P. Vanier 
and in use in this laboratory 
for a number of years. A 
general idea of it may be had 
from Fig. 5. The manner of 
using it is extremely simple. 
The test solution is preserved 
in a one-liter bottle of hard 
glass provided with a doubly 
perforated rubber stopper. 
Through one opening passes 
the siphon tube of the pipette, which is sufficiently long to reach 
to the bottom of the bottle; through the other passes a glass 
tube ending just below the stopper and connected with a small 

* "Air Testing for Engineers," A. G. Woodman and Ellen H. Richards, Tech. 
Quar., 1901, 14, p. 94. 




AIR: ANALYTICAL METHODS 37 

drying tube containing fresh soda-lime. By means of the three- 
way cock the solution is allowed to flow into the small inside 
pipette until it overflows. The stop cock is then turned, and 
the solution allowed to flow out at the lowest point. The pipette 
is made of such a size as to deliver exactly 10 c.c. The excess 
of liquid which accumulates in the overflow reservoir may be 
drawn off when desired. The bottle and pipette are contained 
in a wooden case, about 20 by 8 by 7 inches, outside dimen- 
sions, and with the solution, weigh about eight pounds. The 
case is furnished with a handle at the top so that it may be 
carried readily in the hand from place to place. The bottle 
is fastened to the case, and the lower end of the pipette is 
clamped to a wooden support to keep it from swinging. The 
stopper should be firmly fastened to prevent loosening. 

The bottle should be thoroughly cleaned and washed with 
potassium bichromate and sulphuric acid, and it is best also to 
steam it for half an hour or so. As a further measure of pre- 
caution the rubber stopper is boiled with dilute caustic potash 
and thoroughly washed, although the solution can come in con- 
tact with it only through splashing while the case is being 
carried. 

This measuring apparatus may be used with a variety of 
methods, and with various strengths of solution. 

Cohen and Appleyard Method.* — Principle. — The method 
of Cohen and Appleyard is based upon the fact that if a dilute 
solution of lime-water, slightly colored with phenolphthalein, is 
brought in contact with a sample of air containing more than 
enough carbon dioxide to combine with all the lime present, the 
solution will be gradually decolorized, the length of time re- 
quired depending upon the amount of carbon dioxide present. 
That is, the quantity of lime-water and the volume of air re- 
maining the same in each case, the rate of decolorization will 
vary inversely with the amount of carbon dioxide. 

Reagents and Apparatus. — The solution used is a dilute so- 
lution of lime-water colored with phenolphthalein. To freshly 

* Chem. News, 1894, 70, p. in. 



38 AIR, WATER, AND FOOD 

slaked lime add 20 times its weight of water in a bottle of such 
size that it is not more than two-thirds full. Shake the mix- 
ture continuously for 20 minutes, and then allow it to settle 
over night or until perfectly clear. The resulting solution is the 
stock lime solution, or " saturated lime-water." If made in the 
manner indicated, each cubic centimeter of it ought to be very 
nearly equivalent to one milligram of carbon dioxide. If, how- 
ever, it is desired to know the strength of it more exactly, it 
may be determined by standard acid. 

To prepare the " test solution," pour into the one-liter bottle 
of the testing apparatus one measured liter of distilled water, 
and add 2.5 c.c. of a solution of phenolphthalein (made by dis- 
solving 0.7 gram of phenolphthalein in 50 c.c. of alcohol and 
adding an equal volume of water). Stand the bottle on a sheet 
of white paper and add the " saturated lime-water " drop by 
drop from a pipette, shaking the bottle thoroughly after each 
addition until a- faint pink color is produced which is permanent 
for one minute. Now add 6.3 c.c. of the " saturated lime-water," 
shake, and immediately connect the bottle again to the apparatus. 

For accuracy in air which is high in carbon dioxide, it is found 
advantageous to use a solution which is twice as strong as the 
above. This double solution is prepared in precisely the same 
way, using 5.0 c.c. of the phenolphthalein solution and 12.6 c.c. 
of the " saturated lime-water." 

While this procedure does not give an exact volume of solu- 
tion, it is believed to be the best for the preparation of this 
dilute test solution, since it obviates the necessity for pouring 
the prepared solution from the measuring flask into the bottle 
in which it is kept; 12.6 c.c. of the stock lime solution is added 
rather than 10 c.c, in order to keep the values obtained with 
the resulting solution more nearly comparable with the older 
values calculated on the supposition that 10 c.c. of the " satu- 
rated lime-water " was equivalent to 12.6 mg. of carbon dioxide. 

The apparatus used is that shown in Fig. 5. The samples are 
collected in 500 c.c. bottles by either the water displacement or 
steam vacuum method. 



AIR: ANALYTICAL METHOD 



39 



Procedure. — Remove the rubber stopper from the bottle con- 
taining the sample of air; run in quickly by means of the auto- 
matic pipette 10 c.c. of the standard test solution; note the 
time; replace the stopper; shake continuously and vigorously 
until the pink color disappears; and again note the time. The 
disappearance of color can most easily be seen if the bottle is 
held over a piece of white paper. From the time required for 
the pink color to disappear, the amount of carbon dioxide may 
be found from Table A. 

TABLE A 



Time, 
minutes 

and 
seconds. 


Standard 

solution. 

C0 2 in 

10,000. 


Double 

solution. 
C0 2 in 
10,00c. 


Time, 
minutes 

and 
seconds. 


Double 

solution. 
C0 2 in 
10,000. 


O.I5 
O.30 

0.45 
I. OO 

115 
1.30 

1-45 
2.00 

2.15 
2.30 

2-45 
3.00 

3-15 
3-3o 
3-45 
4.00 

4-i5 
4-30 
4-45 
5.00 

5-3o 


12. I 
9.9 
8.4 
7.2 

6.3 
55 

4-9 

4-4 
4.0 
3-8 
3-7 
3-6 




5-45 
6.00 

6.15 
6.30 

6.45 
7.00 

7-i5 
7 30 


4.0 

39 
.„„.. 

3-7 










16 

13 
11 
IO 

9 
8 

7 
7 
6 
6 
5 
5 
5 
4 
4 
4 
4 
4 
4 




1 

4 

1 • 
1 

3 
6 


5 

1 

7 
4 

1 

9 

7 
5 
3 
2 

1 



Shaker Methods. — At least two forms of apparatus are on 
the market for determining the percentage of carbon dioxide by 
measuring the amount of air required to decolorize the stand- 
ard solutions described on page 38. These are known as the 
Fitz and the Wolpert Shakers (see Fig. 6) . The results obtained 
are less accurate and more uncertain than by other methods, 
but if great care is taken to keep the apparatus at some 






4° 



AIR, WATER, AND FOOD 




distance from the face of the worker, approximate results can 
be obtained. As both shakers operate on the same principle 
only the Fitz will be described. It consists of a tube of about 
30 c.c. capacity, closed at one end, and graduated for a dis- 
tance of 20 c.c. from the closed end. In this 
tube, by means of a rubber collar, slides a smaller 
tube which is contracted at the outer end so as 
to be more readily closed by the ringer. 

Procedure. — See that the inner tube of the 
shaker slides readily in the outer one, moistening 
the rubber collar slightly if necessary. Have 
the inner tube pressed down to the bottom of 
the larger one and measure into the apparatus 
10 c.c. of the test solution from the automatic 
pipette. Pull the inner tube up to the 5 c.c. 
mark (the bottom of the inner tube serving as 
the index) and close the end of the tube with 
the finger. Hold the apparatus horizontally, 
and shake it vigorously for exactly 30 seconds. 
The amount of air that is thus brought in contact with the 
solution is equivalent to approximately 30 c.c, as there are 
25 c.c. of air above the liquid when the small tube is forced to 
bottom of the larger. Remove the finger, press down the small 
tube again to the bottom of the larger and draw it up to the 
20 c.c. mark. Shake the apparatus again for 30 seconds. The 
amount of air brought in contact with the solution is now 
30 + 20 = 50 c.c. Repeat the shaking, using 20 c.c. of fresh 
air each time, until the pink color is discharged. The amount 
of carbon dioxide corresponding to the number of cubic centi- 
meters of air used will be found in Table B. 

Carbon Monoxide. — The detection and estimation of carbon 
monoxide in the very minute quantities in which it is found in 
the air of ordinary rooms is a problem of considerable difficulty. 
Detection. — Probably the most convenient test for detecting 
small quantities is the blood test. Dilute a large drop of human 
blood, freshly drawn by pricking the finger, to 10 c.c. with water. 



Fig. 6. Fitz 
Shaker 



AIR: ANALYTICAL METHODS 



41 



Divide the solution into two equal portions, and shake one 
portion gently for 10 minutes in a bottle containing about 
100 c.c. of the air to be tested. Compare the tints of the two 
portions by holding them against a well-lighted white surface. 
The presence of carbon monoxide is indicated by the appear- 



TABLE B 



Cubic centimeters 
of air. 



50 

70 

90 

IIO 

130 

I50 

170 
I90 
2IO 
230 
250 
270 
290 
3IO 
330 
3SO 
370 
390 
4IO 
4SO 
49O 
530 



Standard test 

solution. 
C0 2 in 10,000. 



Double 

solution. 
C0 2 in 10,000. 



ance of a pink tint in the blood which has been shaken with air. 
One part in 10,000 can be detected in this way.* The delicacy 
of the test can be increased by examining the blood, after shak- 
ing with air, with a spectroscope. By collecting the sample in a 
eight-liter bottle and examining it in this way 0.01 part in 10,000 
may be detected. 

Determination. — Practically all the methods for the determi- 
nation of carbon monoxide in small amounts depend on the 
equation : 

I2O5 + 5CO-+5CO2 + I2; 

* Clowes, "Detection and Estimation of Inflammable Gas and Vapor in the 
Air," p. 138. 



42 AIR, WATER, AND FOOD 

then either the iodine * is titrated or the carbon dioxide deter- 
mined. The method consists of passing the air through U-tubes 
containing potassium hydroxide and sulphuric acid to remove 
unsaturated hydrocarbons, hydrogen sulphide, etc., and then 
through a U-tube containing iodine pentoxide, and heated to 
150 C. The iodine liberated is absorbed in a solution of potas- 
sium iodide, and may be titrated with N/1000 sodium thiosul- 
phate, or the carbon dioxide passing through the potassium 
iodide may be absorbed by barium hydroxide and determined.! 

Nitrites. — The determination of the amount of nitrites or 
nitrous acid in the air can be readily made as follows: Collect 
a sample of the air in a calibrated eight-liter bottle, as in the 
determination of carbon dioxide. Add 100 c.c. of approxi- 
mately N/50 sodium hydroxide solution. (This should be free 
from nitrites, and is best made by dissolving metallic sodium 
in redistilled water.) Shake the bottle occasionally and let it 
stand for about 24 hours. Take out 50 c.c. of the solution and 
determine the amount of nitrites as directed in the determination 
of nitrites in water. 

Micro-organisms.f — The determination of bacteria in the 
air is of importance only under special conditions which some- 
times exist in dairies, factories, etc. In general the method used 
is to filter a measured amount of air through sand, shake out 
the bacteria with sterile water, and plate aliquot portions. 
Counts are made after 5 days' incubation at 20 C. 

* Kinnicutt and Sanford, /. Am. Chem. Soc, 1900, 22, p. 14. 
Morgan and McWhorter, /. Am. Chem. Soc, 1907, 29, p. 1589. 
Seidell, J. Ind. Eng. Chem., 1914, 6, p. 321. 
Gautier, J. Gas Lighting, 121, p. 547. 
f For details of the methods reference should be made to the above articles. 
Recently a portable apparatus has been described by Goutal, Analyst, 1910, 35, 
p. 130. 

t See "Standard Methods for the Bacterial Examination of Air," Am. J. Pub. 
Health, 1910, 6, No. 3, or reprint by the Am. Pub. Health Assn. 



CHAPTER IV 

water: its relation to health, its sources and properties 

Two-thirds of the animal organism consists of water; this 
water is necessary * for practically all physiological processes, 
either taking part in the reaction or acting as a solvent. It aids 
in carrying nourishment to all parts of the body and in disposing 
of the waste products formed. The evaporation of water from 
the surface of the body serves as the most important method 
of regulating the body temperature. Since water is lost by 
these means as well as during respiration, it is evident that the 
animal organism must be supplied with water from outside 
sources. The daily amount needed for each person is five or 
six pints. This water is derived in part from food which, as 
eaten, contains from 30 to 95 per cent; in part from boiled 
water, as in tea and coffee; or raw from well or city tap. 

Water is also required for many other purposes, such as cook- 
ing, washing, generation of power, and other manufacturing 
uses. It has been estimated that 25 gallons per'person per day 
is sufficient for household purposes. Then some must be al- 
lowed for public use and a rather large amount for manufactur- 
ing. For cities in this country amounts varying from 50 to 
200 gallons are used, with an average of close to 100 gallons. 
This is about three times as much as is used in European cities, 
and undoubtedly a large amount represents unnecessary waste. 
That this is true is shown by the fact that when the individuals 
in a community are required to pay for the actual amount of 
water consumed, which is done through the introduction of 
meters, the consumption falls off to one-half or one-third of the 
former quantity used. Waste of water represents a very serious 
problem in large cities, where it is often necessary to go long 

* See " Text-book of Physiological Chemistry," Abderhalden-Hall, John Wiley 
& Sons, 1908, p. 354. 

43 



44 AIR, WATER, AND FOOD 

distances at great expense, to obtain a sufficiently large supply 
suitable for drinking purposes. 

The problem is made still more difficult by the use of large 
bodies of water, both lakes and rivers, for the purposes of waste 
disposal. Recent reports of experts * have raised the question 
as to how much of the expense of purifying a sewage should be 
borne by the community emptying its waste into a stream, and 
how much should be borne by a community farther down the 
stream where water is removed for domestic use. The only 
certain condition which should be demanded is that wastes 
should be in such a state and so diluted that no nuisance will 
be created along the banks of the stream. It seems as if the 
question of further purification would have to be decided for 
each individual case as it arises. 

That there is a close relation between drinking water and 
disease has long been suspected, but it is only since the develop- 
ment of the present ideas of the cause of disease that this 
relationship has been satisfactorily demonstrated. Drinking 
water may act as the carrier of the germs of at least two well 
defined diseases, — Asiatic cholera and typhoid fever, — and 
probably of those of other intestinal troubles. There is, be- 
sides, some tendency to disturb the system when a change is 
made from one kind of drinking water to another of radically 
different composition, such, for example, as a change from a 
hard Middle West water to a soft New England water. The 
disturbance is generally only temporary, as the system becomes 
rapidly accustomed to new conditions. 

The first cholera epidemic to be traced definitely to drinking 
water was that in London in 1854, which centered about the 
Broad Street Pump, and the investigation of which was thor- 
oughly carried out by an efficient health officer. Since then 
numerous epidemics have been traced to the use of polluted 
water, notably that of Hamburg in 1892-3.! 

* See, for example, Eng. Rec, 191 2, 65, p. 209. 

t For a description of epidemics of both cholera and typhoid fever see Sedg- 
wick's "Sanitary Science and Public Health." 



WATER 45 

In this country we have little to fear from cholera on account 
of the efficient work of the Public Health Service at our ports, 
but typhoid fever is still a scourge and a disgrace. As early as 
1850 it was maintained by Budd in England that this fever was 
spread by drinking water, but no sufficient evidence was pro- 
duced until the Lausen, Switzerland, epidemic of 1872. The 
first large epidemic in this country to be traced to water was that 
of Plymouth, Pa., in 1885, in which about 1000 cases resulted 
from the negligence of an attendant on one typhoid patient. 
Since that time numerous small and large epidemics have been 
traced with more or less certainty to the use of polluted water. 

That the introduction of a good water supply in place of a 
bad one results in a marked decrease in typhoid fever can be 
readily seen by almost endless lists of statistics of cities and 
towns which have either obtained a new supply or have intro- 
duced niters, the deaths from typhoid being from one-half to 
one-rlfth of the number formerly recorded in such places.* 

Xot only does the introduction of unpolluted water mean a 
decrease in typhoid fever, but there seems also to be a general 
increase in the health of the community. This effect was 
noticed at about the same time by Mills in this country and 
Reincke in Germany, and is known as the Mills-Reincke phe- 
nomenon. Hazen attempted to formulate a mathematical re- 
lationship between the decrease in typhoid fever and that in all 
other diseases, but the result is merely an approximation. This 
increase in the general health may be due to increased vitality 
by the elimination of one disease. It has been recently sug- 
gested that since tuberculosis is liable to follow typhoid fever, 
a decrease in the latter would account for a decrease in the 
former. 

Safe water, is, therefore, one of the necessary requirements of 
any community, large or small. 

Rain Water. — Let us trace the cycle through which water 
passes, and point out the sources of supply, and the methods of 
contamination. Water vapor rising from the sea and land con- 

* See Am. J. Pub. Health, 1913, 3, p. 1327. 



46 AIR, WATER, AND FOOD 

denses and falls to the earth as rain. As it does so, ammonia, 
carbon dioxide, and other soluble gases are absorbed, and dust 
and living organisms are collected. As soon as these sub- 
stances are removed from the air, the rain water becomes a 
very pure source of supply, and can be used for drinking pur- 
poses if properly stored. There are several factors to be ob- 
served in this. First, there should be no connection whatever 
between the storage tank and any drain or sewer from a house 
or barn. More than one case of typhoid fever has resulted 
from the backing up of sewage through an overflow pipe into a 
rain water tank. Second, no metal or other material which 
is injurious to health should be used in building such a tank, 
as rain water is soft and often slightly acid and, therefore, 
has considerable solvent power for most metals. The best ma- 
terials to use are cement, slate, or stoneware; lead should be 
absolutely avoided, and zinc will not last any length of time. 
Third, there should be some method of wasting the first rain 
that falls, in order not to load the storage tank with dirt and 
other material which may come from a roof or collecting shed, 
and render the water unpalatable. Fourth, there should be 
some easy means of cleaning the tank, and this should be done 
at frequent intervals. Rain water is used for drinking practi- 
cally only in tropical regions. 

Surface Waters. — Approximately one-third of the rain evapo- 
rates again from the surface where it falls; another third runs 
off on the surface, forming streams, rivers, and lakes, finally 
reaching the ocean; the other third sinks into the ground, per- 
haps joining the surface waters underground, coming out as 
springs or flowing wells, or remaining in the soil. The average 
rainfall for the whole United States is about 36 inches, varying 
in different parts of the country from almost nothing to 60 
inches. Thus we find the amount of water with which we have 
to deal is very variable, depending on the locality and the 
season. Approximately one-half of the rainfall finds its way 
finally into rivers, either running off on the surface, or entering 
from underground. 



WATER 47 

Surface waters form an exceedingly important source of 
supplies, as most large cities find them necessary on account 
of the large quantities of water required. Water from small 
streams and brooks on a water shed may be collected and stored 
in reservoirs. This method is considerably used, particularly in 
hilly regions, and if proper care is taken to prevent any pollution 
on the watershed, sufficient supplies of excellent quality may be 
obtained. The reservoirs are generally uncovered, and should 
be stripped of all plant life. Surface water, if unpolluted, 
usually improves on storage. 

Where it is not possible to obtain a supply in this manner, 
large rivers or lakes are used. These are nearly all subject to 
more or less pollution, and in general the water should not 
be used unless filtered or sterilized. Some self-purification will 
take place in such bodies of water.* The most important 
factor in such purification is the removal of bacteria by means 
of sedimentation, the larger particles in the water carrying 
bacteria with them to the bottom of the stream where the patho- 
genic varieties soon die out. Thus in a slow moving stream 
harmful organisms are removed more quickly than in a rapidly 
moving river. Another important factor is the exhaustion of 
the food supply. Also, conditions of temperature are not favor- 
able for the growth of many bacteria, and it is undoubtedly 
true that even in a highly polluted water there is little multi- 
plication, and much dying off of disease organisms. 

On the other hand, it is not safe to rely on self-purification, 
particularly when the health of a large number of people is at 
stake. There are too many possibilities of accidental pollution. 
Some artificial means must be used. These will be mentioned 
later. 

Odors sometimes develop in stored water as a result of growth 
of various plants and animals.f Some of these odors are ex- 

* See Jordan, "Natural-purification of Streams." Paper presented at the 26th 
annual convention of the American Water Works Assn. 

t See Whipple, "The Microscopy of Drinking Water," John Wiley & Sons, 
1914. 



48 AIR, WATER, AND FOOD 

ceedingly disagreeable and may render a water supply unfit to 
deliver. The growths can generally be exterminated by the 
proper use of copper sulphate in quantities which will kill the 
small organisms but are not injurious to the human system (one 
part to from one to 20 million parts of water). 

Surface waters often have color, produced usually by solu- 
tion, in colloidal form, of partly decomposed vegetable matter, 
which is perfectly harmless, and such waters should not be con- 
demned unless sewage is also present. They are, however, often 
decolorized, before delivery, by means of alum. Surface waters 
are generally softer than ground waters, have a slight, but not 
disagreeable odor, may be more or less turbid, and in the sum- 
mer time are liable to be warmer than is desirable. On the 
whole, however, there is no more satisfactory supply for a large 
city than a good surface water. 

Ground Waters. — From 25 to 40 per cent of the annual rain- 
fall in temperate regions soaks at once into the ground, and 
passing downward through the soil to hardpan, to clayey or 
impervious layers, or to rock surface, thence through crevices, 
broken joints, or glacial drift-deposits to the water-table, flows 
along the slope for many miles until it finds its way again to 
the surface, either from the bottom of a lake, the bed of a river, 
the side of a hill, supplying wells or appearing as springs. In 
any one of these courses it may be intercepted by man and 
caught or pumped for his use. Such water may never have 
been far from the surface; it may have been used and returned 
to the ground many times; it may have appeared as surface- 
water and again disappeared to great depths. It has been esti- 
mated that water moves in the ground at rates varying from 
0.2 to 20 feet per day. This movement is in the form of a sheet, 
and its rapidity as well as the amount of water held in the 
ground will depend on the geological formation. Thus a clay 
will hold more water than loam or sand, while the permeability 
is just the reverse, clay being nearly impermeable. Water also 
passes through channels in rocks, either made by the water it- 
self or consisting of cracks and fissures. These latter are often 



WATER 49 

a source of danger, as no purification can take place if a pol- 
luted water travels in this manner. 

This long contact with rocks will, of course, bring mineral 
substances into solution which may be precipitated as new 
rocks are reached or other streams encountered, so that the 
same gallon of water may have had many stages in its course, 
and may have held many different substances in solution. It is 
no wonder that so active a solvent as water should take with it 
much substance whenever it remains long in contact with soil 
or rock, for it may be months before that which has once sunk 
out of sight again appears. In fact, great rivers are supposed to 
flow into the sea from under the surface. Then, too, the acquisi- 
tion of dissolved gases favors the solution of many substances; 
for instance, water carrying carbon dioxide dissolves limestone. 

From a chemical standpoint ground waters may be divided 
into two classes, — (i) springs and shallow wells (those 30 feet 
or less in depth) and (2) deep and artesian wells. In general 
springs and shallow wells yield softer water than deep wells of 
the same region, but they are much more subject to pollution 
than the latter, which, if built so as to exclude any surface 
water, are usually a safe source of supply. Pollution does 
sometimes enter a deep well, due to the passage of water 
through fissures and crevices in the rocks. 

The greatest source of danger is the shallow well. This should 
never be used in a thickly populated region, and in country 
districts only when it can be placed in such a position that there 
can be no connection through the ground with a privy or cess- 
pool. A well should be built in such a manner that no surface 
water can enter it, and the walls should be tight to a depth of 
five to 10 feet below the surface in order that any water which 
sinks into the ground may be sufficiently filtered before enter- 
ing the well. The area from which a well may draw varies 
with the permeability of the soil, and may have a diameter of 
20 or more times the depth of the well. The ground which is 
influenced by a well is in the form of an inverted cone whose 
apex is at the bottom of the well. 



50 AIR, WATER, AND FOOD 

If a well is found upon examination to be polluted with sew- 
age it is often desirable to find the source of trouble in order 
to stop further pollution. There are several methods of doing 
this.* A survey of the ground and the conditions surrounding 
the well is often sufficient to indicate the probable sources, but 
more definite evidence may be required. Some substance is 
then added to the suspected source, washed into the ground 
with a large amount of water, and the well examined for the ap- 
pearance of the substance. For this purpose bacteria, such as 
B. prodigiosus and B. violaceous, can be used. These organisms 
are easily grown, are harmless and can readily be identified. 
If these do not reach the well from the suspected source of 
pollution it is fair to assume that no pathogenic organisms 
will do so, but will be filtered out in passing through the 
ground. The only uncertainty with this method is that while 
the bacteria may be sufficiently removed at the time of the test, 
the filter may sometime break down and allow sewage organ- 
isms, and possibly disease germs, to enter the well. It is, there- 
fore, better not to use a well water which receives sewage from 
any nearby source, even though bacteria are being eliminated 
in passing through the ground. 

Other methods of tracing the source of pollution are by the 
use of common salt, easily tested in the well water by an analysis 
for chloride; lithium or strontium salts, recognized even in 
minute amounts by means of the spectroscope; and fluorescent 
dyes such as fluorescein, which are readily observed in a glass 
of water. 

One method of obtaining ground water in comparatively 
large quantities is by means of the so-called " filter gallery." 
This consists of a series of wells dug near the banks of a river. 
It was originally thought that a suction would be created so as 
to draw water from the river into the wells through a layer of 
soil sufficient to remove harmful bacteria. As a matter of fact, 
the filter gallery actually operates by intercepting ground water 

* See Thresh, "Examination of Waters and Water Supplies," 2nd edition, pp. 
25-34. 



WATER 51 

on its way to the river, really a better method than had been 
intended. In sparsely populated regions where the ground 
water is unpolluted, good results have been and are being ob- 
tained by the filter-gallery, but when a region becomes thickly 
settled considerable danger results. Furthermore, in times of 
drought water may be drawn from the river bed, and if this 
reaches the gallery improperly filtered, a typhoid epidemic 
may result.* 

In general, good ground waters contain more mineral matter 
than surface waters, have no color or odor, can be delivered at 
a lower temperature, and are often more palatable than surface 
waters. It is, however, more difficult to obtain large supplies 
from the ground, and, therefore, only comparatively small com- 
munities can avail themselves of such sources. 

Water Purification. — Water in passing through the ground 
may undergo a number of changes in its dissolved and suspended 
constituents. If this water contains sewage it will carry, with 
other suspended matter, a large number of bacteria, some of 
which may be of pathogenic varieties. If the polluted water 
passes through not too coarse soil, the bacteria will be held by 
the soil, and thus dangerous disease germs will probably be re- 
moved. Even if all the sewage bacteria are not removed there 
will still be some protection against disease, because disease 
organisms have, in general, less vitality to withstand unfavor- 
able conditions as well as being present in smaller numbers than 
less harmful varieties. However, there is still some chance of 
these bacteria being present at times, and it is, therefore, not 
advisable to use water in which sewage organisms are present. 

In streams, as has already been noted, pathogenic bacteria 
gradually settle to the bottom and die out. 

Thus there is some natural protection against the spread of 
disease by means of drinking water, but it is not safe to depend 
on such protection, particularly where the health of a com- 
munity of people is involved. If a water supply which is sub- 

* See "Typhoid Fever in Des Moines, Iowa," /. Am. Med. Assn., 1911, 56, 
p. 41. 



52 AIR, WATER, AND FOOD 

ject to either continuous or intermittent pollution has to be 
used, some method of artificial purification is required before it 
can be safely used for drinking purposes.* 

There are two general methods of filtering water on a large 
scale. The first is known as slow sand filtration. In this 
method the water is run through a layer of sand from two to 
four feet thick, supported by gravel and properly underdrained. 
The filter beds are generally built in units of one acre each, and 
may be covered or not depending on the climatic conditions. 
Previous to filtration the water may be screened and stored in 
reservoirs to allow some removal of suspended matter, includ- 
ing bacteria. As the water passes through the sand a layer of 
slimy material gradually collects on the surface, which acts as 
the real straining medium and holds the bacteria. As this 
material collects the rate of filtration decreases until a point is 
reached where it is uneconomical to continue. The water is 
then allowed to drain out from the sand, the top layer scraped 
off, and the filter again started. The sand removed is washed 
and returned to the filter about once a year. A slow sand filter 
operates at rates of from one and a half to three million gallons 
per acre per day, and is probably the most efficient method of 
removing bacteria on a large scale. It does not, however, com- 
pletely remove color or odor. 

The other method is that known as rapid filtration (also, un- 
fortunately, termed mechanical filtration). Instead of allowing 
the filtering layer to form from the matter in the water as in 
slow sand filtration, a coagulant, generally alum, is added to 
the water. The alkali, originally present, or added, precipi- 
tates aluminum hydroxide which coagulates the suspended par- 
ticles and removes the color. Part of the hydroxide is allowed 
to settle out and the remainder is put on a filter built of sand, 
where it collects on the surface and forms the filtering medium. 
The filters are washed about every eight hours by reversing the 
flow of water and agitating the sand by means of rakes or com- 
pressed air. Filtration takes place much more rapidly by this 

* See Hazen, "The Filtration of Public Water Supplies." 



WATER 53 

method, being at rates from ioo to 150 million gallons per acre 
per day. If there is insufficient alkali present naturally in the 
water enough must be added, usually either as sodium carbon- 
ate or as calcium carbonate, to completely precipitate the alum 
and leave some alkali in excess. Alum, being acid, if allowed 
to remain in the water renders it corrosive. The amounts of 
alum used vary from one-tenth to three grains per gallon of 
water. 

Rapid filtration does not give quite as high a bacterial removal 
as slow filtration, but it is much more efficient in removing 
turbidity and particularly color. It requires a smaller invest- 
ment and occupies less ground for the same amount of water 
filtered. With either method expert control is necessary in 
order to obtain satisfactory results. 

A number of filters on the same principle as just described, 
but built in small units, are on the market, intended to supply 
hotels, manufacturing establishments, swimming pools, etc. 
Many of them give reasonably good results when properly 
operated, but they never should be considered to be automatic 
in character. They all need careful attention. 

Filters still smaller are sold for office and household uses. 
These generally consist of artificial stone or porcelain through 
which the water is forced, such as the Pasteur-Chamberlain or 
the Berkefeld filter. If the stone, or candle as it is called, is in 
good condition, sterile water may be drawn when the filter is 
first put into use, but the bacteria lodging in the stone grad- 
ually develop and may grow through the filter so that as water 
passes through it will wash bacteria with it. It must be ad- 
mitted that the chances are that pathogenic organisms will not 
get through. If, however, there is a crack in the candle, often 
too small a one to be visible, the filter will allow all kinds of 
bacteria to pass. One of the great objections to the use of such 
filters is the false feeling of safety which they may inspire in 
the owners. The all too common small " filter" which screws 
on the faucet is not only useless, but worse. 

If unsafe drinking water must be used in a house, the only 



54 AIR, WATER, AND FOOD 

sure method is to bring the water to a boil. This is sufficient to 
kill any harmful intestinal organisms. Small stills which can 
be placed on the back of the stove are of service in this con- 
nection. The flat taste of boiled water may be removed by the 
addition of a pinch of salt or by aeration. 

Sterilization of Water. — Where a badly polluted supply is 
used, or extreme caution is desirable, or where a good supply 
suddenly becomes polluted and emergency measures deemed 
wise, disinfection may be resorted to. The most practical 
method is by the use of compounds of chlorine, — hypochlorite 
of lime (chloride of lime or bleaching powder), sodium hypo- 
chlorite (electrolytic bleach), or chlorine gas itself. Of these 
the cheapest under ordinary conditions is chloride of lime. 
This has the disadvantage of being disagreable to handle, and 
of not dissolving completely in water. Amounts of from -^ to 
t 3 q grains per gallon are generally sufficient. Sodium hypo- 
chlorite can be used where there is cheap electricity, as it is 
made by passing a current through a solution of common salt. 
The use of chlorine gas is a recent development and appears to 
be giving satisfactory results, although considerably more ex- 
pensive than the other methods. 

None of these substances, in the quantities used, are in any 
way harmful. Where large doses are given complaints are 
sometimes received that they can be tasted in the water, but, 
even if true, this is not a necessary consequence of their use. 
The disinfecting action is probably due to the chlorine itself. 

Electrical methods of sterilization are also in somewhat 
limited use. One of these is through the formation of ozone by 
an electrical discharge through air, and treatment of the water 
with the ozonized air. Ozone, in the presence of water, is a 
reasonably good disinfectant, but its cost makes it prohibitive in 
most places, and its application to the water presents some 
engineering difficulty. The largest plant working is probably 
that at St. Petersburg.* 

A more recent development than ozone is the use of ultra- 

* See Tillmans-Taylor, "Water Purification and Sewage Disposal." 



WATER 55 

violet light, as obtained by the quartz-mercury- vapor lamp. 
Ultraviolet light is a good disinfectant, but it is expensive to 
produce in most places, and there are difficulties in applying it 
to waters of all characters. The rays will not penetrate a turbid 
or colored water to any extent, and, therefore, preliminary filtra- 
tion and decolorization is often necessary. This, of course, adds 
greatly to the expense. The method may, however, find use in 
the future, if it is possible to produce it for a reasonable amount. 
Ice. — Questions are often asked concerning the use of ice 
in drinking water. In general, natural ice, particularly when 
stored from four to eight months, is comparatively safe. In 
freezing, suspended and dissolved matter is not removed from 
the water with the ice, except a small amount mechanically 
enclosed. Furthermore, it has been shown that over 90 per 
cent of sewage bacteria die out on storage. Artificial ice, if 
made from polluted water, is not safe, as in the method used all 
suspended matter is frozen into the center of the cake. If the 
artificial ice is made from unpolluted or from distilled water 
as it should be, it is, of course, perfectly safe to use for all 
purposes. 



CHAPTER V 

SAFE WATER AND THE INTERPRETATION OF ANALYSES 

Pure water, such as may be found in the laboratory, is neither 
necessary nor probably desirable for drinking. There are, how- 
ever, certain requirements which should be borne in mind in 
looking for a supply. First, the water should be free from sew- 
age and all other waste products. Second, it should not con- 
tain an excessive amount of mineral matter. Third, it should 
be free from color, odor, taste and suspended matter, and 
should be delivered at a temperature not over 15 C. It is 
obvious that all of these requirements cannot always be lived 
up to, but it is essential that the first one should be, even at the 
expense of the other two. A water free from sewage and other 
waste products can be called a "safe" water. Unfortunately, 
physical appearance is taken as the criterion of the safety of a 
supply by too many people. The cool, clear, colorless water is 
much to be preferred to the safe colored or muddy one; and it 
is sometimes difficult to persuade the user of such a supply as 
the former that he may be endangering his health by drink- 
ing it when tests have shown the presence of sewage. Since 
appearance is of such importance, it is necessary to take this 
into account in any water examination. 

Since, as already described, a water once in contact with 
sewage may become purified and be rendered safe for drinking 
purposes, and since water is so universally made a carrier of 
refuse that it is difficult to find a stream or well which has never 
been at any time in contact with waste, certain arbitrary stand- 
ards have been chosen to determine when a water may be called 
safe, on the basis of an analysis. Such limits are very mislead- 
ing of themselves, especially if used over a wide extent of ter- 
ritory. The English standards, for instance, are not applicable 

*6 



SAFE WATER 57 

to eastern North America. Only a study of all local conditions 
and a wise interpretation of all results can make standard 
figures of any significance. This is true, also, of bacterial re- 
sults in surface waters. In lakes and streams there are so 
many varieties of bacteria present and in such varying numbers, 
according to wind and rain and water-shed, that taken alone 
the numerical count gives no more convincing proof than is 
found in chemical figures. 

While it is quite within the limits of possibility that a cul- 
ture-tube of typhoid bacilli might be emptied into the middle 
of a river or be washed into a reservoir, and chemical analysis 
give no sign, yet no continuous natural means of contamination 
is known which is not accompanied by substances readily de- 
tected by suitable chemical examination. 

Sanitary Examination. — The examination of a water to de- 
termine its safety for domestic use is called a sanitary analysis, 
in distinction from that examination which determines its fit- 
ness for manufacturing purposes, for use in steam boilers, or its 
medicinal value. Such an examination may be either bacterio- 
logical or chemical in character, but the object in either case is 
the same, that is, to determine the absence of sewage or its 
presence in quantities sufficient to render the water dangerous 
to drink. In neither kind of examination are the harmful sub- 
stances themselves sought for. Typhoid organisms have been 
isolated from water during epidemics in only a few cases and 
the process is a long and tedious one. Furthermore, such a 
search would often be useless for an infected person does not 
usually come down with the disease until 10 to 14 days after 
infection, and the organisms might have died during this time. 
Also, one does not care to wait until an epidemic starts before 
examining the water supply, but desires to know in advance 
whether or not there is any possibility of trouble. The presence 
or absence of sewage determines this possibility. 

In a bacteriological examination, the presence of sewage is 
determined first, by counting the total number of bacteria per 
cubic centimeter, and second, by looking for some type of dis- 



58 AIR, WATER, AND FOOD 

tinctly sewage organism, such as B. coli. The total count has 
little significance in a surface water, but in a well or filtered 
water, should not be over ioo bacteria per cubic centimeter. 
B. coli should not be present in numbers of one or more per 
cubic centimeter. Considerable discussion surrounds the de- 
termination of this organism, but it is quite impossible to see 
what difference it makes whether the bacteria isolated show all 
the typical reactions of B. coli communis or not. The members 
of the colon group get into a water supply practically only with 
sewage, and it should not make any difference in the interpre- 
tation of results, as to what particular member of that group is 
found. For the methods of making these determinations the 
reader is referred to some book on bacteriology.* 

Before proceeding with the laboratory test of a water, it is 
essential to know something of the surroundings of the source 
of supply. So long as the eye can re-enforce the other tests and 
the whole course of the water may be clearly traced, it is com- 
paratively easy to judge of the character of a supply and of its 
safety for human use; but when a hole in the ground is the 
visible source, or the actual history of the water is hidden in 
unknown distances and depths, the diagnosis is more difficult. 

The geological horizon and superficial soil must be studied; 
the direction and flow of underground water, not the slope of the 
surface only; the possible sources of danger, occasional as well 
as constant, within at least a quarter of a mile radius. The 
composition of unpolluted water of the same region should 
always be at hand for consultation. 

An examination of the environment is often sufficient to con- 
demn a water, but cannot usually give it a clear certificate. 
Laboratory tests should follow. In the next paragraphs will 
be found a discussion of the interpretation of sanitary chemical 
analyses. 

Expression of Results. — Results of a sanitary chemical 
analysis should be expressed in parts of any particular substance 

* Prescott and Winslow, " Elements of Water Bacteriology." John Wiley & 
Sons, New York, 1913. 



SAFE WATER 59 

per million of water. In most cases this is equivalent to milli- 
grams per liter — the exceptions being where the water has an 
appreciable specific gravity above i.o, such as sea water. 

Accuracy of Methods. — In all water analyses very minute 
quantities are sought after, and, therefore, all the tests applied 
must be exceedingly delicate in character. The quantitative 
results need not, however, be of great percentage accuracy. 
For example, it makes no particular difference whether 0.050 
or 0.055 parts of ammonia per million of water are found — an 
error of 10 per cent. It might make a good deal of difference 
if one found 0.2 of a part or 0.05 — a difference of 0.15 parts 
per million, an amount which in most analytical work would be 
entirely negligible. The American Public Health Association 
has suggested that only a limited number of figures be used in 
reporting an analysis, and thereby ehminate any impression of 
false accuracy. 

Above 10 parts per million. Use no decimals. 

From 1 to 10 parts per million. Use 1 decimal. 
From 0.1 to 1 part per million. Use 2 decimals. 

In the determinations of ammonia and of nitrites 3 decimals 
may be used. 

The above discussion does not mean that the analyses should 
be made in a careless or slipshod manner, in fact, quite the re- 
verse is true, for there is no kind of chemical work which requires 
greater care or cleanliness. 

As little time as possible should elapse between the collection 
and examination of samples of water. The more polluted the 
water the more rapidly will changes take place, and, therefore, 
all samples should be tested within 24 hours of their collection. 
Samples for bacterial analysis should be examined immediately, 
or if sent to a laboratory, should be packed in ice. Sewages and 
sewage effluents should be analysed within six hours of collec- 
tion, or if for chemical analysis should be chloroformed (5 c.c. 
per liter) to prevent chemical changes taking place. 

Chemical Examinations. — The chemical analyses generally 
made in sanitary work are the following: nitrogen as free am- 



60 AIR, WATER, AND FOOD 

monia, as albuminoid ammonia, as nitrates, and as nitrites; 
chlorides in terms of chlorine; oxygen consumed; soap hard- 
ness; total solids and loss on ignition; iron; and sometimes 
oxygen dissolved. The interpretation of the results of each of 
these will be discussed, and where possible, standard figures will 
be given. 

Nitrogen Cycle. — The most important determinations which 
must be made in order to decide on the potability of the water 
in question are those involving the nitrogen compounds and 
chlorides. A clear understanding of the cycle of nitrogen in 
nature is, therefore, necessary. 

Nitrogen is present in living plants and animals mainly in 
the form of organic compounds — the proteins and simpler 
amino compounds. These substances, if boiled with alkaline 
potassium permanganate, will give off part of the nitrogen in 
the form of ammonia which can be collected and determined 
quantitatively. This is called " albuminoid ammonia." When 
the living plant or animal dies, the proteins are attacked by 
bacteria and putrefy. In this process the nitrogen is converted 
first into simpler amino bodies and finally into ammonium salts 
or substances, such as urea, which readily yield ammonia. Thus, 
the determinations of ammonia (called "free" ammonia) and 
of albuminoid ammonia will indicate how far this putrefaction 
has gone. A waste product, such as sewage, will give, when 
fresh, both free and albuminoid ammonia in quantity, but on 
standing, some of the organic nitrogen will change to ammonia, 
so that the free ammonia will increase and the albuminoid am- 
monia decrease. Thus, these analyses may be used to indicate 
fresh or recent sewage pollution of a water supply. 

When the organic nitrogen is largely converted to ammonium 
compounds, and if oxygen is present, another kind of bacteria, 
called the nitrosomonas, will act on the latter substances and 
oxidize them to nitrites. This is the second stage in the nitrogen 
cycle. Thus, the presence of nitrites in a water may indicate 
less recent pollution than the presence of only free ammonia. 

The nitrites, however, are not stable, and if sufficient oxygen 



SAFE WATER 6 1 

is available, they are oxidized by still another set of micro- 
organisms, the nitrobacter, giving nitrates. The nitrifying bac- 
teria remained undiscovered for some time, owing to the fact 
that they do not grow in the laboratory on any medium con- 
taining large amounts of organic matter. Thus, the presence of 
nitrates in a drinking water may indicate contact with sewage 
at some past time, or as it is called, past pollution. 

Nitrates are food for green plants, which in turn die or are 
eaten by animals, the nitrogen being changed from the inor- 
ganic back to the organic form, and the cycle thus completed. 

But the cycle is not so simple as would appear. Nitrogen 
may be lost from it in two ways. While ammonia is being oxi- 
dized to nitrites, both may be present and interaction may 
result with the formation of nitrogen gas. 

NH 3 + HN0 2 -> N 2 + 2 H 2 0. 

Or, nitrites may be reduced by micro-organisms with the liber- 
ation of nitrogen. Nitrates may also be reduced to nitrites by 
bacteria, iron, or possibly by organic matter. 

Nitrogen may be added to the cycle as well as lost from it. 
This takes place by means of the nitrogen-fixing bacteria which 
occur largely in nodules on the roots of leguminous plants, such 
as the clover, and also in some soils. These have the power of 
removing nitrogen from the air and making it available for the 
plant. 

Practical use is made in the septic or ImhofT tanks of the 
ability of micro-organisms to decompose organic matter and the 
modern sewage filter is really a culture bed for the development 
of nitrifying organisms which act on the sewage and render it 
stable by oxidizing the nitrogen compounds to nitrates. 

As will be seen from the above discussion, a sanitary chemical 
analysis depends primarily upon the determination of the con- 
dition of the nitrogen compounds in a sample of water. Each 
of these will be discussed separately. 

Albuminoid Ammonia. — This is the ammonia which is set 
free by the action of boiling alkaline potassium permanganate 



62 AIR, WATER, AND FOOD 

on nitrogenous organic matter. This may have entered the 
water from perfectly harmless sources, such as dead vegetable 
substances, or it may have come from waste material, such as 
sewage. If from the former source, it is relatively stable and, if 
present in any quantity, is accompanied by color in the water. 
If from sewage, there may be little or no color, and the nitrog- 
enous matter will be relatively unstable. The stability can be 
determined by the action of the permanganate, stable substances 
yielding ammonia only slowly and unstable substances losing it 
rapidly. 

The albuminoid ammonia gives no accurate measure of the 
total nitrogenous organic matter present, as only about 50 per 
cent is converted to ammonia, but it does give a good indica- 
tion of whether or not the organic matter is easily decomposed, 
and, therefore, whether or not it comes from sewage. A color- 
less water should not contain over 0.15 parts per million of 
nitrogen as albuminoid ammonia. The amounts found in good 
ground waters are generally much lower than this figure. 
Samples from storage reservoirs, in which there is plant life, may 
contain larger amounts — up to 0.4 of a part. 

The total organic nitrogen as determined by the Kjeldahl 
method is sometimes used in place of the albuminoid ammonia, 
but it gives no means of distinguishing between stable and un- 
stable substances, and is not considered in this country to be as 
good an index of pollution. 

Free Ammonia. — This is the ammonia which comes off from 
a water on direct distillation, the water being made alkaline if 
necessary. The ammonia is probably present as ammonium 
salts. Since this represents the first stage in the decomposition 
of unstable nitrogenous organic matter, its presence in abnormal 
quantities may be taken as an index of sewage pollution. The 
amounts of ammonia present in good waters are generally very 
small, and amounts over 0.15 to 0.2 parts expressed in terms of 
nitrogen are sufficient to indicate pollution. In general, the free 
ammonia is less than the albuminoid ammonia. If the reverse 
is found it is an indication of trouble, unless both are very low. 



SAFE WATER 63 

Cases sometimes arise where abnormally high free ammonia 
does not indicate sewage, and the analyst should continually be 
on the lookout for these exceptions. One may be found in wells 
dug in glacial drift, where ammonia may have come from fossil 
remains. Another occurs sometimes when a well is located in 
close proximity to an ammonia refrigerating plant. 

Nitrites. — Nitrites in a water are formed either from the oxi- 
dation of ammonia or the reduction of nitrates. In either case, 
they represent an unstable condition, usually accompanied by 
large numbers of bacteria, and in most cases sewage pollution 
or surface contamination. As has been said, "a state of change 
is a state of danger," and the presence of nitrites reveals this 
condition. As has been mentioned, nitrites may be formed 
from nitrates by reduction due to iron or organic matter, but 
such cases are not at all usual. 

A good drinking water should be either entirely free from 
nitrites or should contain them only in very minute quantities. 
Amounts of 0.01 to 0.02 or more parts per million of nitrogen 
are sufficient to condemn a water. But while the presence of 
abnormal amounts of nitrites indicates danger, their absence is 
no guarantee of the purity of a supply. 

Nitrates. — As seen from the discussion of the nitrogen cycle, 
nitrates are the final stage in the oxidation of nitrogen com- 
pounds. Since they are food for plants, we would expect to 
find only small amounts where there is any plant life. Thus, 
surface waters are generally low in nitrates while ground waters 
may be higher. It is probable that practically all nitrates in 
waters have come originally from animal matter, as vegetable 
nitrogen is not easily oxidized. In some cases, nitrates have 
been known to come from chemical fertilizers used on fields. 

High nitrates, combined with high chlorides, indicate past 
pollution. "Past" is used either in the sense of time or dis- 
tance. That is, fresh sewage may have found its way into a 
well at some time past, and the nitrogen compounds may have 
remained there, and been oxidized until, at the time of examina- 
tion, nitrates predominated over the other forms. Or the sew- 



64 AIR, WATER, AND FOOD 

age may have come from such a distance that oxidation has 
taken place in the passage through the ground. 

The presence of high nitrates is not generally accompanied 
by sewage bacteria, and, therefore, immediate danger from the 
supply does not exist. The objection to using such waters for 
drinking is, first, that if pollution has once entered, it may enter 
again, and, second, that the natural filter through which the 
water is passing may, at some time, fail to work properly and 
allow sewage bacteria, and with them possibly typhoid organ- 
isms, to enter the water. In other words, past pollution indi- 
cates a condition of possible future danger, and it is safest to 
avoid this either by not drinking such water or by watching it 
carefully by means of frequent examination. 

Good surface waters are low in nitrates, over i part of nitrogen 
as nitrate per million of water being a suspicious sign. Ground 
waters often run much higher than this even when unpolluted, 
but above 5.0 parts, is in most cases, sufficient to condemn the 
water as unsafe for drinking. 

Chlorides. — In interpreting the results of the analyses of the 
various nitrogen compounds, it must be remembered that the 
presence of any one of them in abnormal amounts is rarely 
sufficient evidence upon which to declare a water unfit to drink. 
The nitrogen compounds must be accompanied by an abnormal 
amount of chlorides. Chlorides occur in waters principally as 
the sodium salt, and as the results of analysis are. generally ex- 
pressed in terms of chlorine, this latter term is the one in common 
use. Human urine contains about 1 per cent sodium chloride, 
and the amount of sewage entering a well or stream can be ap- 
proximately determined by the rise in the chlorine content. 
Furthermore, chlorine passes through no such cycle as that of 
nitrogen, and common salt is not taken up by most plants, so 
that once in a water there is no way by which the chlorine can 
entirely disappear. If, then, abnormal amounts of chlorine 
accompanied by abnormal amounts of one of the nitrogen com- 
pounds are found in a water, it is a pretty sure indication that 
sewage, in some state, is entering. 




STATE BOARD OF HEALTH 
MAP OF THE 

The lines represent normal chlorine. 

STATE OF MASSACHUSETTS. Tto fleures show ob8e " ed ch,OTines which - 



SHOWING 

NORMAL CHLORINE. 



%&&■* x o w T 




C o at 



& JZ C 



STATE BOARD OF \ 

MAP OF THE 

STATE OF MASSAC 

SHOWING 

NORMAL CHL 



SAFE WATER 65 

The difficulty is to decide on what constitutes an abnormal 
amount of chlorine, since salt occurs, to some extent, in most 
soils and rocks, and in some places in very large quantities. 
Some years ago, the Massachusetts State Board of Health at- 
tempted to solve this problem by a careful study of a large 
number of waters from all over the state. The chlorine was 
determined in those which, from the surroundings and the other 
constituents, could safely be regarded as free from pollution. 
The figures obtained were placed on a map of the state at the 
appropriate places and lines drawn through equal values. These 
lines were termed "isochlors." This map is shown opposite. 
(Note. The figures are given on the map in parts per 100,000.) 
Since this map was made for Massachusetts, a number of other 
states have made similar ones. The maps give with reasonable 
accuracy the normal chlorine values for surface waters, but for 
deep or artesian wells, the figures do not necessarily hold. Con- 
sequently, in some states, for example in Illinois, it has been 
found more satisfactory to give normal values according to the 
source of the supply. 

But the presence of chlorine in amounts above normal, alone, 
is not sufficient to condemn a water. High chlorine and low 
nitrogen are sometimes found together in a well water which 
has been contaminated with wastes from a sink drain. The 
ratio of nitrogen to chlorine can sometimes be used to distin- 
guish between barn and human sewage, as the former contains 
less chlorine than the latter for the same amount of nitrogen. 
Excessively high nitrates with chlorine only slightly above 
the normal sometimes indicates washings from a fertilized 
field. 

Mineral Matter. — Since water is a universal solvent, it is not 
surprising to find considerable amounts of mineral matter under 
the headings " total solids" and " hardness." How much cal- 
cium sulphate or magnesium chloride or other soluble mineral 
matter is allowable in a potable water is for the physician rather 
than the chemist to say, but it seems to be the consensus of 
opinion that, for the normal healthy person, the presence of 



66 AIR, WATER, AND FOOD 

mineral matter, even in considerable quantities, is in no way 
deleterious to the system. 

As has been said, the human system possesses great adapta- 
bility, not only for different foods, but for mineral substances 
water-carried. Not so the steam-boiler or the laundry- tub, 
which reacts very sensitively and affects the pockets of the 
consumers. The determination of sulphates gives an indi- 
cation as to how the hardness is divided, as permanent hard- 
ness is caused principally by calcium sulphate. 

In a region of soft water, high solids with chlorine and nitrates 
indicate sewage pollution. Silica is much more commonly 
present, even in surface-waters, than is often supposed. What 
its effect may be is unknown. Iron is not uncommonly found in 
combination with organic matter in either surface or imperfectly 
filtered waters in contact with soils poor in calcium salts. It is 
frequently accompanied by free ammonia, which causes an 
abundant growth of Crenothrix. It is also present in deep wells 
in the form of bicarbonate, which precipitates on exposure to 
warm air. 

Organic Matter. — The amount of carbonaceous matter, de- 
termined either by the oxygen-consumed test or by the loss on 
igniting the solids, is of little use in interpreting a water analysis; 
it is too difficult to get concordant results. The latter test may 
sometimes be of service in a qualitative way, because the residue 
from a recently polluted water often gives a distinctive disa- 
greeable odor when ignited. In some laboratories, the quan- 
titative determination is omitted entirely. 

Dissolved Oxygen. — During the last few years, the determina- 
tion of the oxygen dissolved in water has assumed considerable 
importance, because of the use of the test as an indication of 
the sanitary condition of a harbor or river. As long as sufficient 
oxygen is present, the putrefactive changes which give off dis- 
agreeable odors will not take place. There is some difference of 
opinion as to how low the oxygen content may be allowed to fall 
and still prevent these changes, but 40 per cent of saturation is 
a safe figure to use. 






SAFE WATER 67 

The test is also used to determine the putrescibility of a 
sewage effluent as described later under that test. The object 
is to determine the amount of oxygen absorbed by the organic 
matter in the effluent. 

Physical Tests. — These are of little importance as far as the 
determination of pollution is concerned, but are generally in- 
cluded in an examination in order to satisfy those who insist 
that a water shall be attractive as well as safe. 

Sewage Analysis. — Sewages may be tested to determine 
their strength and constituents in order to help in deciding upon 
the best method of treatment, and also as a basis for determin- 
ing the amount of purification which any process gives. The 
analysis of effluents is carried on also for this latter purpose, and 
in order to determine their putrescibility. For an extended 
discussion the reader is referred to another book.* 

Value of Tests. — It is often asked if some tests cannot be 
made by the ordinary person of average intelligence which 
will enable him to tell the quality of a water as well as the 
expert to whom he pays ten or twenty dollars for an opinion. 
A careful perusal of the preceding pages will have answered 
the question in the negative. There is no assay of water as 
there is of gold and silver. Not one, but ten or twenty tests 
must be made. Not only must the tests be made with the 
utmost care and cleanliness of person, utensils, and room, but 
the results must be studied in the light of other experience and 
other knowledge, geological and biological, and after all this is 
done, there is an array of circumstantial evidence which must 
be carefully weighed by one whose judgment and experience 
enable him to read clearly where another might see nothing. 
The value of a water-analysis is in direct proportion to the 
knowledge and experience of the one who interprets it. Clinical 
skill in addition to theoretical knowledge is as much required 
to interpret the figures obtained in the course of a water-analy- 
sis, as in the diagnosis of a disease; and the analogy goes still 
further, for just as some diseases are clearly defined, and others 

* Fowler, " Sewage Works Analysis." 



68 AIR, WATER, AND FOOD 

are so complicated that only those who have had long experience 
can outline a safe course of treatment, so some waters bear the 
marks of their character so plainly as not to admit of mistake, 
while others require most careful study. For these reasons, the 
value of water-analysis should not be decried because the fears 
aroused by reports given by unskilled analysts prove ground- 
less, any more than the practice of medicine should be discarded 
because inexperienced men make mistakes. 

Is the water in any given case safe for drinking? To answer 
this question there is needed a knowledge, wider than a chem- 
ist's, of the relation of decaying organic matter and of the 
germ-carrying power of water to outbreaks of disease. There 
must be added the knowledge of the biologist, the engineer, 
and the sanitarian. 



CHAPTER VI 

water: analytical methods * 

Water-analysis cannot be carried on in an ordinary labora- 
tory. In order to obtain satisfactory results, it is necessary to 
have a room set apart for the purpose, and to exclude rigidly all 
operations which tend to the production of fumes or dust. 
Where such minute traces of substances are dealt with as in 
water-analysis, too much care cannot be taken to insure the 
absolute cleanliness of the apparatus and the surroundings. It 
is desirable that the room be well lighted, and, if possible, the 
windows should face toward the north. 

For the collection of water samples, glass-stoppered bottles of 
about a gallon capacity are best. Those used in this laboratory 
are of white glass, 15 inches high to the top of the stopper, five 
and a half inches in diameter, and weigh about three pounds. 
They have flat, mushroom stoppers, on each of which is engraved 
a number to correspond with that on the bottle. The bottles, 
before being sent out, are thoroughly cleaned with potassium 
bichromate and sulphuric acid, washed with distilled water and 
dried. If glass-stoppered bottles are not at hand, new demi- 
johns fitted with new corks may be used. A glass bottle or a 
demijohn is much to be preferred to an earthenware jug, because, 
if for no other reason, it is so much easier to be sure that the 
interior is clean. It should always be borne in mind that in 
water-analysis the question is one of very minute quantities of 
material, and that the methods to be employed are extremely 
delicate. Hence, in the case of many waters, careless handling 
of the sample would contaminate the water to a sufficient ex- 
tent to render valueless the results obtained in the laboratory. 

* See "Standard Methods for the Examination of Water and Sewage," Ameri- 
can Public Health Association, 1912. 

69 



70 AIR, WATER, AND FOOD 

In collecting samples, the following directions should be closely 
followed:* 

Directions for Collecting Samples for Analysis. — From a 
Water-tap. — Let the water run freely from the tap for a few 
minutes before collecting the sample. Then place the bottle 
directly under the tap and rinse it out with the water three 
times, pouring out the water completely each time. Place it 
again under the tap; fill it to overflowing and pour out a small 
quantity so that there shall be left an air-space under the stopper 
of about an inch. Rinse off the stopper with flowing water; 
put it into the bottle while still wet and secure it by tying over 
it a clean piece of cotton cloth. Seal the ends of the string on 
the top of the stopper. Under no circumstances touch the in- 
side of the neck of the bottle or the stem of the stopper with 
the hand, or wipe it with a cloth. 

From a Stream, Pond, or Reserooir. — Rinse the bottle and 
stopper with the water, if this can be done without stirring up 
the sediment on the bottom. Then sink the bottle, with the 
stopper in place, entirely beneath the surface of the water and 
take out the stopper at a distance of twelve inches or more be- 
low the surface. When the bottle is full replace the stopper, 
below the surface if possible, and secure it as directed above. 
It will be found convenient, in taking samples in this way, to 
have the bottle weighted so that it will sink below the surface, 
and to remove the stopper with a cord. It is important that the 
sample should be obtained free from the sediment at the bottom 
of a stream and from the scum on the surface. If a stream 
should not be deep enough to admit of this method of taking a 
sample, dip up the water with an absolutely clean vessel and 
pour it into the bottle after the latter has been rinsed. 

The sample of water should be collected immediately before 
shipping by express, so that as little time as possible shall inter- 
vene between the collection of the sample and its examination. 
All possible information should be furnished concerning the 
source of the water and of possible sources of contamination. 

* Ann. Rept. Mass. State Board of Health, 1890, p. 520. 



WATER: ANALYTICAL METHODS 71 

For example, in the case of a well, the proximity of dwellings, 
cesspools, or drains should be recorded, and the character and 
slope of the soil, whether toward or away from the well, should 
be noted. In the case of a surface-water, mention any ab- 
normal or unusual conditions; as, for instance, if the streams 
or ponds are swollen by recent heavy rains, or are unusually low 
in consequence of prolonged drought, or if there be a great deal 
of vegetable growth in or on the surface of the water. Record, 
in short, any circumstantial evidence which by any possibility 
may aid in the final judgment. 

The question of proper collection of samples is an important one, 
and the chemist is perfectly justified in refusing to give an opinion 
in regard to the purity of a water which he has not himself collected. 

Preparation for Analysis. — Since changes in the composition 
of a contaminated water are constantly going on, the analysis of 
the sample should be begun without delay. The bottle is held 
under the tap, and the neck and stopper are washed free from 
adhering dust. The stopper is rinsed off with some of the water 
from the bottle. 

If the sample has stood for several hours, allowing suspended 
matter to settle, the conditions of turbidity and sediment, as de- 
scribed on page 108, may first be observed. The sample is then 
thoroughly mixed and qualitative tests made for alkalinity, 
ammonia and chlorides. Make the alkalinity test with methyl 
orange indicator. If a sample is acid, it is necessary to make 
alkaline, as described later, before starting the determinations 
for free ammonia and chlorides. Make the test for ammonia 
by adding two c.c. of Nessler reagent to 50 c.c. of the sample in 
a Nessler tube. A reddish-brown color or precipitate means the 
presence of large amounts of ammonia, and care should be taken 
not to take too much of the sample for the quantitative deter- 
mination (see page 74). A qualitative test for chlorides will 
determine the amount of water to be taken for the analysis, — 
a very slight opalescence meaning low chlorides, which will 
necessitate the use of a 250-c.c. sample, while a distinct tur- 
bidity or a precipitate will allow a 25-c.c. sample to be used. 



72 AIR ? WATER, AND FOOD 

As the nitrogen compounds are more subject to important 
changes than any others, it is desirable to make these determi- 
nations first, the order of the remainder being immaterial. 

It is essential that the sample of water be thoroughly mixed 
each time any is withdrawn, as only in this way will the samples 
removed be of constant composition. This is particularly im- 
portant in dealing with sewages and sewage effluents, or where 
there is a considerable amount of suspended matter. 

The methods for preparing standard solutions and other 
special reagents will be found in Appendix B. 

Determinations of Free and Albuminoid Ammonia. — Am- 
monia occurs in waters as ammonium salts, — carbonate, chlo- 
ride, or nitrate. In sewages it may be partially present as the 
hydroxide. On boiling an alkaline solution of these substances, 
the salts are decomposed, as well as some unstable organic com- 
pounds such as urea, and ammonia passes off and dissolves in 
the condensed steam. The ammonia thus collected is called the 
" free ammonia." If, now, alkaline potassium permanganate is 
added to the water left after the free ammonia has been removed, 
and the boiling continued, part of the nitrogenous organic mat- 
ter will be decomposed with the liberation of ammonia. This 
is termed " albuminoid ammonia." 

The principles involved in the two determinations have been 
described in the above definitions, that is, the water is first 
boiled, and the steam condensed until all the free ammonia 
has been removed. Then alkaline potassium permanganate is 
added, and distillation continued until no more albuminoid 
ammonia is evolved. The ammonia is determined in the dis- 
tillates by means of Nessler reagent which gives a greenish 
yellow with very small amounts of ammonia, and yellow to red- 
dish brown with larger quantities. The exact amount of am- 
monia is obtained by comparison of the colors obtained with 
those from known amounts of ammonia. 

Nessler reagent is a solution of potassium mercuric iodide 
(K^Hglt) containing potassium hydroxide. The colored sub- 
stance formed when this reacts with ammonia is dimercuram- 






WATER: ANALYTICAL METHODS 



73 



monium iodide (NHg 2 I • H 2 0), which is an ammonium iodide in 
which the hydrogen atoms have been substituted by mercury. 
This substance is slightly soluble in an excess of potassium iodide 
and potassium hydroxide, giving a color proportional to the 
amount of ammonia present. 

Apparatus and Reagents. — The apparatus consists of a 
750 c.c. round-bottomed flask, having square shoulders and a 
narrow neck five inches long, and an ordinary Liebig con- 




Fig. 8. 

denser fitted with a block-tin inner tube T 3 g of an inch in diam- 
eter which extends just through a cork stopper closing the 
flask. The apparatus is set so that the distillate may be col- 
lected directly in a 50 c.c. Nessler tube. The flasks are heated 
either with the free flame of a Bunsen burner or with an electric 
flask heater. These latter are somewhat slow in heating up 
and in cooling, but give an even heat with just about the proper 
rate of distillation and show little tendency to cause " bump- 
ing." In place of the Liebig condenser, the tin tube may be 
passed through a copper or galvanized iron tank (see Fig. 8), 



74 AIR, WATER, AND FOOD 

fitted with proper inlets and outlets, and serving as a con- 
denser for a number of flasks. New flasks are treated with 
boiling dilute sulphuric acid and potassium bichromate before 
they are used. New corks should be steamed out for one or 
two hours. A good sound cork will last for several months 
with daily use. 

The Nessler tubes used should be of the same height up to 
the 50 c.c. mark. 

Reagents necessary are Nessler solution, alkaline potassium 
permanganate, a standard ammonium chloride solution and 
ammonia-free water (see Appendix B). 

Procedure. — Free the apparatus from ammonia by placing 
500 c.c. of ammonia-free water in the flask and distilling. Col- 
lect the distillate in 50 c.c. Nessler tubes, and test each tube as 
it is filled, by adding two c.c. of Nessler reagent and comparing 
the color obtained after waiting five minutes with that obtained 
by adding two c.c. of Nessler reagent to 50 c.c. of ammonia-free 
water. This latter gives a zero standard. Continue until the 
distillate is free from ammonia and then pour the water left in 
the flask into the bottle marked " ammonia-free residues." 

While this is going on make a qualitative test on the sample 
of water to determine the amount which should be used for the 
quantitative determination. To do this, add to 100 c.c. of the 
water, removed from the bottle only after thorough mixing, 
one c.c. of 10 per cent copper sulphate solution, and one c.c. of 
50 per cent potassium hydroxide. Allow to settle and filter 
through a dry paper into a 50 c.c. Nessler tube, discarding the 
first 10 c.c. of filtrate. Add two c.c. of Nessler reagent, and 
allow to stand for 10 minutes. Make a standard by placing 
two c.c. of the standard ammonium chloride solution in a Nessler 
tube, making up to 50 c.c. with ammonia-free water, mixing 
thoroughly and adding two c.c. of Nessler reagent. If the color 
obtained from the sample of water is less than this standard, 
use a 500 c.c. sample of the water for the determination; if 
equal to or greater than the standard, use a 100 c.c. sample; 
if the color is so deep that a precipitate forms, use a 10-c.c. 



WATER: ANALYTICAL METHODS 75 

sample. For sewages five or 10 c.c. are sufficient. In case less 
than 500 c.c. are used, dilute the amount to this volume with 
ammonia-free water. 

Test some of the water with methyl orange for acidity. If 
acid, 0.5 gram of pure sodium carbonate must be added before 
starting the distillation. The great majority of drinking waters 
are alkaline, but once in a while an acid water turns up, and it 
is well to be on the lookout. Acid sewages and sewage filter 
effluents are not uncommon. 

When the apparatus has been freed from ammonia, shake 
thoroughly the bottle containing the water sample, and measure 
out in a calibrated flask 500 c.c, or a smaller amount, according 
to the qualitative test described above, adding enough ammonia- 
free water to make the total volume at least 500 c.c, and 
pour into the distilling flask. If necessary, add sodium car- 
bonate. Distill three portions of 50 c.c. each into well-rinsed 
Nessler tubes. Regulate the height of the flame so that the 
time of distilling 50 c.c. shall not be more than eight and not 
less than five minutes. In most cases three portions are suffi- 
cient to collect all the free ammonia, but it is well to test the 
last portion with Nessler reagent, and compare it with a zero 
ammonia standard, before proceeding further. Save these por- 
tions for nesslerization, as they contain all the free ammonia. 

After the free ammonia has been distilled off, allow the con- 
tents of the flask to cool for to minutes; then add 40 c.c. of 
alkaline permanganate through a funnel, taking care that none 
of the alkaline solution touches the neck of the flask, and pro- 
ceed with the distillation of the albuminoid ammonia. With 
colored waters distill off five portions of 50 c.c. each; with 
colorless waters, three or four portions will suffice. These 
portions contain the albuminoid ammonia. 

Unless permanent standards are used, prepare standards by 
adding to Nessler tubes nearly filled with ammonia-free water 
varying quantities of the standard ammonium chloride solution; 
for instance, 0.1, 0.3, 0.5, 0.7, 1.0, 1.3, 1.5, 2.0, 2.5, 4.0, 6.0 c.c. 
The standard ammonium chloride solution contains 0.0000 1 gram 



7 6 



AIR, WATER, AND FOOD 



N in one cubic centimeter. Mix the contents of the tubes by ro- 
tating them between the palms of the hands or by pouring into 
another Nessler tube and back again (never shake them like a 
test-tube or stir them with a rod), allow them to stand for a few 
minutes and add two cc. of Nessler reagent to each tube and 
to each of the portions of distillate. At the end of 10 minutes 
match the colors and record the amount of ammonia in terms 
of cubic centimeters of the standard ammonium chloride solu- 
tion. From the value of this solution calculate the amounts of 
free and albuminoid ammonia as parts of nitrogen per million 
of water. 

As an example, the following results from distilling 500 cc. 
may be given. 



Free ammonia. 


Albuminoid Ammonia. 


ist 50 CC 
2nd 50 CC 
3d 50 CC, 


0.7 CC 
0.3 CC 
0.0 CC 


ist 50 cc, 4.5 CC 
2nd 50 CC, 2.8 CC 
3d 50 cc, 1.5 CC. 
4th 50 cc, 1.0 cc 
5th 50 cc, 0.5 cc 


1.0 CC 


10.3 cc 



In this case, the free ammonia would be 0.020 and the albumi- 
noid ammonia 0.206 parts per million. 

In dealing with sewages or sewage effluents, which are very 
high in free ammonia, if the ammonia were collected in three 
portions, so much would distill over in the first portion that the 
color given with the Nessler reagent would often be too deep to 
read or a precipitate might form. To avoid this, the total dis- 
tillate of 150 to 175 cc is collected in a 200-cc graduated flask, 
made up to the mark, thoroughly mixed by pouring into a clean 
dry beaker and back again, and then 50 cc of it taken for 
nesslerization. In this way, the ammonia is distributed more 
evenly in the distillate and the determination is not sacrificed. 

If free ammonia only is desired in a sewage or sewage effluent, 
a direct determination is to be preferred over distillation. For 



WATER: ANALYTICAL METHODS 77 

this, proceed as directed in the qualitative test for ammonia, ex- 
cept that a smaller amount of the filtrate should be used, two 
or five c.c, and this made up to 50 ex. with ammonia-free water, 
treated with Nessler reagent, and matched against standards 
as just described. 

Notes. — Where a large number of determinations are made 
at frequent intervals, permanent Nessler standards are a great 
convenience. These should be made according to directions 
found in " Standard Methods,"* but should be adjusted by 
comparison with nesslerized standards made from ammonium 
chloride solution. 

It is impossible to convert all of the organic nitrogen into 
ammonia by boiling with alkaline permanganate. The amount 
of ammonia which is thus obtained depends not only upon the 
character of the substances, but also upon the concentration of 
the solution and the rate of boiling. In order that the albu- 
minoid ammonia in potable waters shall bear some definite 
relation to the total organic nitrogen, it is necessary that 
conditions shall be duplicated as nearly as possible in differ- 
ent determinations; that is, the alkaline permanganate must Be 
added to a definite volume of water, and the boiling must be 
carried on at a definite rate. Some of the highly-colored surface- 
waters give up their nitrogen very slowly by this treatment; 
polluted waters, on the other hand, yield the ammonia more 
rapidly, so that the observation of the relative amounts found 
in the successive portions is of the utmost importance in form- 
ing a judgment. 

A depth of color given by six c.c. of the standard ammonium 
chloride with the Nessler reagent is about the limit of satisfactory 
comparison in the 11-inch 50 c.c. tubes. The color given by 
10 or 12 c.c. of the standard may be matched in the 100 c.c. tubes 
with a depth of five inches and a diameter of i\ inches. 

For most cases, where great exactness is not essential, it is 
possible to divide the 50 c.c. or the 100 c.c. portion into two 

* "Standard Methods of Water Analysis," American Public Health Asso- 
ciation, 1912, p. 17. 



78 AIR, WATER, AND FOOD 

equal parts by pouring into a tube the exact counterpart of the 
standard tube and matching the color. It is even possible to 
approximate closely the correct result by the use of a foot rule. 
The standard is, we will assume, five c.c. The height of the 
liquid in the tube to be tested we will call nine inches. If the 
height of the column left which matches five c.c. is three inches, 
then the reading was 15 c.c. of the standard. 

The limit of solubility of the mer cur-ammonium iodide is 
reached at 25 or 30 c.c. of the standard in 50 c.c. The incipient 
precipitate not only changes the color of the solution, but causes 
a slight milkiness or turbidity which prevents a sharp reading 
of the color. 

The test is an excellent example of quantitative color work 
when carried out under strictly comparable conditions. 

It should, perhaps, be stated that in both the ammonium and 
nitrate determinations, as also in that of iron, dilution of the 
sample in which the color is already developed does not give a 
correct result. Therefore dilution, if necessary, must be made 
before the reagents are added. 

In order to secure the most accurate results, it is important 
that the temperature of the distillates to be nesslerized and of 
the standards be the same, since the warmer solutions give a 
more intense color with the Nessler reagent. 

Total Organic Nitrogen, Kjeldahl Process. — The principles 
involved in the method consist in the oxidation of the carbon 
and hydrogen of the organic matter with boiling sulphuric acid, 
the nitrogen being converted into ammonia and held by the acid 
as ammonium sulphate. The ammonia is then liberated and 
distilled off from an alkaline solution. 

Apparatus and Reagents. — The apparatus used is that shown 
in Fig. 9. This is an arrangement for distilling with steam. 
The reagents needed are nitrogen-free sulphuric acid and potas- 
sium hydroxide (see Appendix B) . 

Procedure. — Measure 500 c.c. of the water into a round- 
bottomed flask of 750 c.c. capacity and boil until about 200 c.c. 
have been driven off. (The free ammonia which is thus ex^ 



WATER: ANALYTICAL METHODS 



79 



pelled may be determined, if desired, by connecting the flask 
with a condenser.) Allow the water remaining in the flask to 
cool, and add 10 ex. of pure concentrated sulphuric acid free 
from nitrogen. Mix by shaking; 
place the flask in an inclined posi- 
tion on wire gauze under the hood 
and boil cautiously until the water 
is all driven off. Place a small 
funnel in the neck of the flask to 
prevent the escape of acid fumes, 
and continue the heating for at 
least half an hour after the sul- 
phuric acid becomes white. Mean- 
while, rinse out the distilling ap- 
paratus and free it from ammonia 
as usual. Then, after the acid in 
the digestion flask has cooled, rinse 
down the neck of the flask with 
ioo c.c. of ammonia-free water and 
attach the flask to the distillation 
apparatus. Add ioo c.c. of potas- 
sium hydroxide solution through 
the separatory funnel and distill 
off the ammonia with steam, re- 
ceiving the distillate in a 250-c.c. graduated flask. Conduct 
the distillation rather slowly until the first 50 c.c. have distilled 
over, then distill more rapidly until about 175 c.c. have been 
collected. Make the volume of the distillate up to 250 c.c. 
with ammonia-free water, mix it thoroughly and take 50 c.c. 
for nesslerization. 

The use of mercury and of potassium permanganate to assist 
in the oxidation has been found to be unnecessary, as the organic 
matter in natural waters is much more easily oxidized than in 
other substances, — flour, for instance. The presence of nitrates 
and nitrites in waters has not been found to interfere with the 
accurate determination of the organic nitrogen. The error, 




Fig. 9. 



80 AIR, WATER, AND FOOD 

which has been found by Kjeldahl and Warrington to be caused 
by the presence of nitrates seems to disappear when the organic 
material is diluted to the considerable extent that exists in 
natural waters. The high chlorine found in some well-waters 
does not interfere with the method to any extent, but this de- 
termination does not possess much value in this class of waters, 
which are low in organic nitrogen. 

In carrying out the digestion with sulphuric acid, the greatest 
care must be taken to prevent access of ammonia or dust from 
any source. The acid solutions will absorb ammonia from the 
air or from the dust of the laboratory if they are allowed to re- 
main uncovered for any length of time. This source of error 
may in some instances be sufficiently large to render a determi- 
nation valueless, even in a room which is, to all appearances, free 
from ammonia-fumes. Hence, the operation should, if possible, 
be carried to completion within twenty-four hours, and for every 
set of determinations a blank analysis should be made with am- 
monia-free water in order to make a correction for the ammonia 
in the reagents, and for that accidentally introduced during the 
process. 

As the result of many hundred comparative determinations 
of the organic nitrogen and of the albuminoid ammonia in nat- 
ural waters which take their origin in the glacial drift, it has 
been found that the nitrogen given by the albuminoid-ammonia 
process, as directed in the previous pages, is about one-half of the 
total organic nitrogen as given by the Kjeldahl process; in the 
case of sewages and polluted waters, it is very variable owing to 
their irregular composition. 

Determination of Nitrogen in the Form of Nitrites. — This de- 
termination depends on the formation of a pink azo dye by the 
interaction of sulphanilic acid, naphthylamine acetate, and nitrous 
acid. If an excess of the first two reagents is used, the amount 
of dye and, therefore, the depth of color will be proportional to 
the amount of nitrite present in the water. The color is then 
compared with a series of standards made from a sodium nitrite 
solution of known strength and the nitrite computed in terms of 
nitrogen. 



WATER: ANALYTICAL METHODS 8 1 

The reactions which take place are, first, the diazotizing of the 
sulphanilic acid by the nitrous acid present, and then the inter- 
action of this diazo compound with naphthylamine to form the 
colored substance, a-naphthylamine-para-azo-benzene-para-sul- 
phonic acid. 

/NH 2 
CeH4 + Ci H 7 NH 2 + HN0 2 -> 

X S0 3 H 

/ N = N \ 
Ci H 6 C 6 H 4 + 2 H 2 0. 

X NH 2 S0 3 H / 

Apparatus and Reagents. — The only special apparatus needed 
is a number of ioo c.c. Nessler tubes. The reagents used are a 
standard sodium nitrite solution (i c.c. contains o.ooooooi 
gram nitrogen), a solution of sulphanilic acid in acetic acid, a 
solution of naphthylamine acetate, and a suspension of alumi- 
num hydroxide (see Appendix B). 

Procedure. — If the water is colorless, measure out ioo c.c. 
into a ioo-c.c. Nessler tube. If the water possesses color which 
cannot be removed by simple filtration, it should be decolorized 
as follows: Thoroughly rinse with the water a 250-c.c. glass- 
stoppered bottle; pour into it about 200 c.c. of the sample, 
add about three c.c. of milk of alumina and shake the bottle vig- 
orously. Let stand for 10 or 15 minutes and filter through a 
small plaited filter which has been thoroughly washed with 
water free from nitrites. To 100 c.c. of the filtered sample or of 
the originally colorless water add 10 c.c. of the sulphanilic acid 
in acetic acid and 10 c.c. of naphthylamine acetate solution. 
A pink color shows the presence of nitrite. To determine the 
amount* of nitrite present make up standards by placing 5 c.c, 
10 c.c, 15 c.c, and 20 c.c each of the standard nitrite solution 
in ioo-c.c Nessler tubes. Make up to 100 c.c. with nitrite-free 
water, mix by pouring into a Nessler tube and back to the original 
tube, and then add the reagents as before. Allow to stand 10 

* Standard color papers and also acid solutions of fuchsine are used for nitrite 
standards. Neither of these has been found very satisfactory in this laboratory. 



82 AIR, WATER, AND FOOD 

minutes, and match with the color obtained from the water 
sample. If this does not match any of the standard colors, 
make up intermediate standards. Do not attempt to match 
colors closer than to one c.c. of the nitrite solution. If the 
color is deeper than that given by 20 c.c. of the standard nitrite 
solution, start a new determination using a smaller quantity of 
water and diluting to 100 c.c. with the ammonia-free water. 

One c.c. of the standard nitrite solution equals 0.0000001 
gram nitrogen. Determine the number of c.c. needed to match 
the color obtained from the water sample and calculate the 
results in parts of nitrogen per million of water. 

Notes. — In case the color obtained is deeper than 20 c.c. of 
the standard, an aliquot part may be measured, as described 
under the ammonia determination. This will be sufficiently 
accurate for most purposes. 

When once obtained, the color will remain unchanged for one- 
half to three-quarters of an hour. If left for a longer time, the 
nitrites absorbed from the air will noticeably increase the color. 

Determination of Nitrogen in the Form of Nitrates.* — This 
determination depends on the action of nitric acid on phenol- 
disulphonic to form nitrophenoldisulphonic acid, which gives 
an intensely yellow color in alkaline solution. The reactions 
involved can be expressed as follows: 

/ OH / en tt 

C 6 H 3 - SO3H + HNO3 -> C 6 H 2 < ^ 3 £ + H 2 
N S0 3 H 



-OH 
/SO3H 



^N0 2 
/OK 



CeH ^ SO3H+ 3 KOH -> C 6 H 2 < Sgj| + 3 H 2 

N ° 2 \no 2 

Reagents. — The reagents needed are a standard nitrate solu- 
tion of which one c.c. contains 0.000001 gram nitrogen, and phe- 

* Sprengel, Fogg, Ann., 1863, 121, p. 188; Grandval and Lajoux, Compt. rend., 
1865, 101, p. 62; Gill, /. Am. Chem. Soc, 1894, 16, p. 122; Chamot & Pratt, /. 
Am. Chem. Soc, 1909, 31, p. 922; 1910, 32, p. 630; Chamot, Pratt and Redfield, 
/. Am. Chem. Soc, 191 1, 33, p. 366. 



WATER: ANALYTICAL METHODS 83 

noldisulphonic acid (see Appendix B). Care should be taken 
in making this latter reagent as the results are dependent upon 
its composition. 

Procedure. — For ground waters, measure with a pipette two 
samples of the water, one of two c.c. and the other of five ex., 
into three-inch porcelain evaporating dishes and evaporate just 
to dryness on the steam bath or electric plate run at low heat. 
For surface-waters use 10 c.c. If the water is colored, decolor- 
ize with alumina as described under nitrites. Do not allow the 
residue to remain on the steam bath after all the water has been 
evaporated. Cool, add six drops of phenoldisulphonic acid and 
rub with a glass rod to insure complete contact of the acid and 
residue. Then add seven c.c. of distilled water and three c.c. of 
30 per cent potassium hydroxide solution and mix thoroughly. A 
yellow color shows the presence of nitrates. Place this solution 
in a short Nessler tube* for comparison with a standard. This 
standard is prepared as follows: Place one c.c. of potassium hy- 
droxide solution in a short Nessler tube and add standard nitrate 
solution from a burette until the color of the standard nearly 
matches that of the water sample. Make the volumes of the 
two solutions equal by diluting the standard and then add more 
standard nitrate solution until the colors exactly match. Use 
the sample of water for comparison which has the lighter color, 
unless there is no yellow at all. In case the &ve c.c. sample 
gives no color, repeat the determination, using 10 c.c. If this 
gives no color nitrates are absent. If the two c.c. sample gives 
a color which requires more than 10 c.c. of the standard, repeat 
the determination, using smaller amounts of water. 

The standard nitrate solution contains 0.000001 gram N per 
c.c. From the amounts of standard nitrate solution and of 
water used calculate the amount of nitrate present expressed as 
nitrogen in parts per million of water. 

Notes. — High chlorides seriously affect the accuracy of the 
method. This is noticeable in dealing with sea water and deep 
wells which contain large amounts of sodium chloride. In this 
* An ordinary 50-c.c. Nessler tube cut off to a length of about five inches. 



84 AIR, WATER, AND FOOD 

case, the reduction method with alkali and aluminum foil and 
distillation of the ammonia formed, is to be recommended.* For 
most drinking waters it is not necessary to use this method, 
which requires a much longer time than that described above. 

Determination of Chlorine. — Chlorine is present in waters 
in the form of chlorides, and the term " chlorine" is used to 
mean " chlorides " as the results of analysis are given in terms 
of chlorine. 

The determination is made by titration with silver nitrate in 
a solution alkaline with bicarbonates, — the condition generally 
existing in natural waters, — potassium chromate being used as 
an indicator. 

Reagents. — The solutions required are a standard sodium 
chloride solution (i c.c. contains o.ooi gram CI), a solution of 
silver nitrate about one-half as strong, and potassium chromate 
indicator (see Appendix B). 

Procedure. — Standardize the silver nitrate solution by ti- 
trating against a standard sodium chloride solution. To do this 
place 25 c.c. of distilled water in a 6-inch porcelain evaporating 
dish, add three drops of potassium chromate indicator, and then 
run in from a burette a measured amount of sodium chloride 
solution, about five c.c. being sufficient. It is not necessary to 
add exactly five c.c, but it is necessary to know the exact amount 
added. Now add silver nitrate solution from a burette until 
the yellow color of the solution has changed to a faint reddish 
brown. The end point is best seen if 25 c.c. of distilled water 
and three drops of indicator are placed in a 6-inch dish which 
is set beside the dish in which the titration is being carried on. 
This gives a standard color and the end point is reached when 
the solution being titrated shows the slightest appearance of 
red as compared with the standard. From the results of the 
standardization calculate the value of silver nitrate solution in 
terms of sodium chloride solution and in terms of CI per c.c. 

Test the water to be analyzed with phenolphthalein and with 
methyl orange. It should be acid to the former and alkaline 

* See "Standard Methods," p. 25. 



WATER: ANALYTICAL METHODS 85 

to the latter. If alkaline to phenolphthalein neutralize the 
sample measured for titration with dilute sulphuric acid. If 
acid to methyl orange neutralize with sodium bicarbonate. 

Highly colored waters should be decolorized before titration 
as the color interferes with the end point. To do this shake 
some of the sample in an Erlenmeyer flask with milk of alu- 
mina, one c.c. of the latter being used for each 100 c.c. of water. 
Heat the mixture rapidly to boiling, allow to settle and decant 
through a filter. 

Make a qualitative test for chlorides on the sample of water. 
If only a faint opalescence appears, a 250 c.c. sample must be 
used for analysis; if a marked cloudiness or a precipitate is 
formed, a 25 c.c. sample may be used. If the larger sample is 
found to be necessary, evaporate to about 25 c.c. on a steam 
bath or electric plate; avoid boiling. Cool before titrating. 

To 25 c.c. of the water, measured with a pipette, or an evap- 
orated 250 c.c. sample, in a 6-inch porcelain dish, add three drops 
of indicator and about five c.c. of sodium chloride solution, the 
exact amount being measured as in the standardization. Then 
run in silver nitrate solution until the end point is reached, 
using the standard color as before. 

From the amounts of silver nitrate and sodium chloride solu- 
tions used calculate the amount of chlorine present in parts per 
million. 

Notes. — With waters containing large amounts of chlorides, 
the addition of sodium chloride in the titration may be omitted. 

It is important that the process be carried out essentially as 
described, since it has been found that the results vary with 
the volume of solution in which the titration is made, the amount 
of chromate used, and the amount of precipitated chloride pres- 
ent.* 

Determination of the Carbonaceous Matter or " Oxygen 
Consumed." — This determination is supposed to give the 
amount of oxygen absorbed by the organic matter present in 
the water. Except in sewage analysis, the results are of little 

* Hazen, Am. Chem. J., 1889, 11, p. 409. 



86 AIR, WATER, AND FOOD 

importance, and the determination may be omitted without 
appreciably affecting the interpretation of the results of the 
whole analysis. 

The oxygen consumed is determined by allowing an excess 
of potassium permanganate in acid solution to act on the or- 
ganic matter in the water under certain conditions, and then 
titrating the excess of permanganate with ammonium oxalate. 

Equations : 

4 KMn0 4 + 6 H 2 S0 4 + 5 C -> 2 K 2 S0 4 + 4 MnS0 4 + 6 H 2 
+ 5 C0 2 . 

2 KMn0 4 + 3 H 2 S0 4 + 5 C 2 H 2 4 - 2 H 2 -> K 2 S0 4 + 2 MnS0 4 
+ ioC0 2 + i8H 2 0. 

Reagents. — The solutions required are a standard ammo- 
nium oxalate solution (1 ex. equals 0.0001 gram oxygen), a 
potassium permanganate solution of approximately the same 
strength, and 1-3 sulphuric acid (see Appendix B). 

Procedure. KubeVs Hot Acid Method. — Standardize the 
potassium permanganate against the oxalate in the following 
way: Measure 100 c.c. of distilled water into a 250-c.c. flat- 
bottomed flask, add 10 c.c. of sulphuric acid (1-3) and then add 
from a burette a measured quantity (about 10 c.c.) of standard- 
ized potassium permanganate solution. Place the flask on a 
wire gauze or electric stove and heat quickly to boiling. Boil 
the solution gently for exactly five minutes, remove it from the 
flame, cool for one minute, and add from a burette sufficient 
ammonium oxalate to decolorize the solution. Titrate back 
with the permanganate to a faint permanent pink color. Cal- 
culate the value of the permanganate in terms of standard 
ammonium oxalate and of oxygen. 

For the analysis proceed just as in the standardization, re- 
placing the distilled water by the sample to be tested. The 
oxygen consumed value for the water under examination is 
obtained from the number of c.c. of permanganate used in 
excess of that required to react with the oxalate added in the 
determination. Calculate the results in parts of oxygen per 
million of water. 



WATER: ANALYTICAL METHODS 87 

Notes. — For highly colored surface-waters 25 c.c. are taken 
and diluted to 100 c.c. with water free from organic matter; for 
sewages, 10 c.c. or less are diluted in the same way. 

The oxygen given up by the permanganate combines with the 
carbon of the organic matter and perhaps, to a certain extent, 
with the hydrogen, but not with the nitrogen. The amount of 
oxygen consumed bears some relation, therefore, to the amount 
of organic carbon present in the water, but this relation cer- 
tainly cannot be taken as a definite one in every case, the results 
varying even with the time of boiling. The method has its 
greatest value when it is used to compare waters of the same 
general character and having the same origin; for example, in 
making periodical tests of the purity of the effluent from a filter. 
Furthermore, in order that the results shall have this compara- 
tive value, it is absolutely necessary that the process shall 
always be carried out in exactly the same way, even to the 
minutest detail of quantity, time and temperature. 

In some cases it may be found advantageous to heat the solu- 
tion upon the water-bath for half an hour instead of boiling it 
for five minutes. The results, however, will not be exactly 
comparable with those obtained by boiling. 

Different kinds of organic matter behave differently with 
various oxidizing agents, so that a comparison of the results 
obtained with different oxidizing agents may throw light upon 
the character of the organic matter, as well as its amount.* 
In waters from the watersheds of eastern North America the 
color and the oxygen consumed have a certain, though some- 
what varying, relation. 

Determination of the Residue on Evaporation and the Loss 
on Ignition. — Procedure. — Carefully clean a large platinum 
dish, ignite for a few minutes over a burner, cool in a desiccator 
and weigh. Measure into it 100 c.c. of the water (200 c.c. in 
the case of surface-waters), and evaporate to dryness on the 
water-bath. When the water is all evaporated, heat the dish 
in the oven at the temperature of boiling water for one hour, 

* Woodman, /. Am. Chem. Soc, 1898, 20, p. 497. 



88 AIR, WATER, AND FOOD 

cool in a desiccator over sulphuric acid, and weigh. The increase 
in weight gives the "total solids" or "residue on evaporation." 

The residue should be ignited and the loss on ignition noted. 
Heat the dish in a "radiator," which consists of another plat- 
inum dish enough larger to allow an air-space of about half an 
inch between the two dishes, the inner dish being supported by 
a triangle of platinum wire. Over the inner dish is suspended 
a disc of platinum-foil to radiate back the heat into the dish. 
The larger platinum dish is heated to bright redness by a triple 
gas-burner. An electric muffle may be used in place of the radi- 
ator. This should be run at a temperature of about 500 C. 
Heat the dish until the residue is white or nearly so. Note any 
blackening or charring of the residue and any peculiar "burnt 
odor" which may be given off. After the dish has cooled, 
slightly moisten the residue with a few drops of distilled water. 
Heat the residue in the oven for an hour; cool in a desiccator 
and weigh. This gives the weight of "fixed solids," the differ- 
ence being the "loss on ignition." Save the residue for the de- 
termination of iron. 

Notes. — Before the introduction of modern methods of water- 
analysis, the determination of "loss on ignition" was the only 
method for the estimation of organic matter in water. In 
order, however, that the determination shall possess any real 
value, it is necessary to regulate carefully the heat during the 
ignition, so as to destroy the organic matter without decompos- 
ing calcium carbonate or volatilizing the alkali chlorides. 

This is what the use of the radiator or muffle is intended to 
accomplish, and in the case of surface-waters with low mineral 
content and considerable organic matter, the method gives gen- 
erally satisfactory results. But in the case of ground waters 
having little or no organic matter and high mineral content, 
the loss is often very great on account of the decomposition of 
nitrates and chlorides of the alkaline earths and the loss of water 
of crystallization. In waters of this class, the determination of 
"loss on ignition" is, therefore, generally meaningless, although 
an approximation to the amount of organic matter can be ob- 



WATER: ANALYTICAL METHODS 89 

tained by the addition of sodium carbonate to the water before 
evaporating to dryness. By this means, the alkaline earths are 
precipitated as carbonates, the chlorine and nitric acid are held 
by an alkaline base, and there is no water of crystallization in 
the residue. Even with this modification, the loss is consider- 
able when magnesium salts are present, owing to the evolution of 
carbonic acid. 

It is the practice in some laboratories to ignite over a direct 
flame, taking care that the dish does not reach a temperature 
above a faint redness. 

The behavior on ignition is oftentimes significant. Swampy 
or peaty waters give a brownish residue on evaporation to dry- 
ness, which blackens or chars, and this black substance burns 
off quite slowly. The odor of the charring is like that of char- 
ring wood or grain; sometimes sweetish, but not at all offensive. 
Waters much polluted by sewage blacken slightly; the black 
particles burn off quickly and the odor is disagreeable. Any 
observations on this point should be recorded in the report. 

Determination of Iron. — This depends on the color produced 
by the action of potassium sulphocyanate on ferric chloride. 
The color obtained is compared with standards. 

Reagents. — The solutions needed are a 1-1 hydrochloric 
acid, a potassium sulphocyanate solution, and a standard iron 
solution made from ferrous ammonium sulphate, one c.c. of 
this containing 0.0001 gram iron (see Appendix B). 

Procedure. — Treat the residue from the loss on ignition, or 
that obtained by the evaporation of 100 c.c. of the water, with 
five c.c. of 1-1 hydrochloric acid, warming on the steam-bath 
or hot plate so as to dissolve as much as possible of the mineral 
matter. Wash the solution with distilled water into a 100-c.c. 
Nessler tube, filtering if there is any insoluble matter. Make 
up to about 50 c.c. with distilled water. Add potassium per- 
manganate solution, a few drops at a time, until the solution 
remains pink for 10 minutes. This is to oxidize any ferrous 
chloride to the ferric condition. Then add 10 c.c. of potassium 
sulphocyanate solution and make the volume up to the 100 c.c. 



90 AIR, WATER, AND FOOD 

mark with distilled water. Iron gives a red color. If iron is 
present prepare a blank standard by placing 75 c.c. of distilled 
water, five c.c. of hydrochloric acid and 10 c.c. of potassium 
sulphocyanate solution in a 100 c.c. Nessler tube. Now add 
from a burette, standard iron solution until the color nearly 
matches that obtained in the determination. Fill the tube with 
distilled water to the 100 c.c. mark and continue adding the iron 
solution until the color of the blank exactly matches that of the 
determination. From the number of c.c. of standard iron solu- 
tion used calculate the amount of iron in the water. 

Notes. — In the case of some river-waters, it will be found 
necessary to add a few cubic centimeters of hydrochloric acid 
to the water while evaporating, in order to facilitate the solution 
of the iron. This should be done on a separate portion from that 
used for the determination of total solids. 

The colors should be matched immediately after adding the 
sulphocyanate, since the color fades appreciably on standing. 
If the color is greater than that given by 3.5 c.c. of the standard 
solution an aliquot part should be used. In this case sufficient 
hydrochloric acid and potassium sulphocyanate should be added 
so that the same amounts of these are present as given in the 
above directions. 

Determination of Hardness. — Soap (Clark's) Method. 
This method really gives the soap consuming power and not 
the true total hardness, but it is in general use for sanitary pur- 
poses, and where the water is to be used for household purposes 
only, really gives what is most wanted. The determination 
depends on the fact that soap forms an insoluble precipitate 
with the calcium and magnesium salts in the water. As soon 
as the precipitation of the latter is complete a permanent lather 
is formed. This serves as the end point. The hardness is 
expressed in terms of calcium carbonate per million. 

Reagent. — A standard soap solution (see Appendix B) . 

Procedure. — Measure 50 c.c. of water into a 200-c.c. clear 
glass-stoppered bottle and add the soap solution from the burette, 
two or three tenths of a cubic centimeter at a time, shaking well 



WATER: ANALYTICAL METHODS 91 

after each addition, until a lather is obtained which covers the 
entire surface of the liquid with the bottle lying on its side, and 
is permanent for five minutes. The number of parts of calcium 
carbonate corresponding to the volume of soap solution used is 
found in the table in Appendix A. 

Notes. — The importance of adding the soap in small quan- 
tities cannot be too strongly emphasized, especially in the pres- 
ence of magnesium compounds. The presence of magnesium 
salts will be recognized by the peculiar curdy appearance of 
the precipitate formed and by the occurrence of a false end point, 
the lather lasting about three minutes when the titration is 
about half done. 

By reference to the table it will be observed that values are not 
given for more than 16 c.c. of the soap solution. If in any case 
the water under examination requires more than 10 c.c. of the 
standard soap solution, a smaller portion of 25 c.c, 10 c.c. or 
even two c.c, as the case may require, is measured out and made 
up to a volume of 50 c.c with recently distilled water. If the 
volume of soap used is always about seven c.c, this will keep 
the results comparable with each other, although the element 
of dilution introduces an error. Potable waters, in the eastern 
United States, at least, are rarely so high in mineral matter as 
to require excessive dilution. In the case of extremely hard 
waters, however, the acid method is to be preferred. Distilled 
water itself, containing no calcium salt whatever, requires the 
use of a considerable quantity of soap to produce a permanent 
lather. The cause for this seems to exist in the dissociation 
of the greater part of the soap at the extreme dilution to which 
it is subjected, and the slow accumulation of a sufficient quantity 
of undissociated soap to allow of the increase of surface tension 
to a point at which soap-bubbles will persist. 

Hehner's Acid Method* — The temporary hardness of a water 
is that part of the total hardness which can be removed by 
boiling. It is due to the presence of the bicarbonates of calcium 

* Hehner, Analyst, 1883, 8, p. 77; Draper, Chem. News, 1885, 51, p. 206; Ellms, 
/. Am. Chem. Soc, 1899, 21, p. 239. 



92 AIR, WATER, AND FOOD 

and magnesium. These give an alkaline reaction to indicators 
such as methyl orange and erythrosine, and can be titrated 
with standard acid. The results obtained will differ slightly 
from the true temporary hardness, on account of the solubility 
of calcium and magnesium carbonates which are formed when a 
solution of the bicarbonates is boiled, but the results are close 
enough for practical purposes. 

Permanent hardness is that which is not removed by boiling, 
and is due mainly to the presence of the sulphates and chlorides 
of calcium and magnesium. After removing the temporary 
hardness by boiling, the permanent hardness, i.e., the calcium 
and magnesium remaining in solution, may be determined by 
adding standard "soda reagent" (a mixture of equal parts of 
sodium hydroxide and sodium carbonate), which precipitates 
the magnesium as hydroxide and the calcium as carbonate. 
The excess of soda reagent added is then determined by titration 
with standard acid, — the amount consumed representing the 
calcium and magnesium. 

If the original water is neutralized with sulphuric acid all the 
temporary hardness will be converted to permanent hardness. 
If this latter is then determined, it will represent the total hard- 
ness of the sample of water. 

Reagents. — The solutions required for the hardness deter- 
minations are N/20 and N/50 sulphuric acid, N/10 soda reagent, 
methyl orange indicator and, for some purposes, erythrosine. 

Procedure for Alkalinity. — Measure 200 c.c. of the sample, 
filtered if necessary, into a porcelain evaporating dish, add two 
drops of methyl orange indicator and titrate to a faint pink with 
N/50 sulphuric acid. The end point can best be seen by placing 
200 c.c. of distilled water in another dish and adding two drops 
of indicator. This gives a standard color and the first change 
of the sample being titrated, toward a pink color, can be readily 
recognized. The number of c.c. of acid used multiplied by five 
gives the alkalinity in parts of calcium carbonate per million. 
Save the titrated sample for the determination of total hardness. 

If the soap hardness is over 300, a 100 c.c. sample should be 



WATER: ANALYTICAL METHODS 93 

used. In this case multiply the c.c. of acid by 10 to get the 
alkalinity. 

Notes. — If the water to be tested has been treated with alum, 
erythrosine indicator must be used as methyl orange is not 
sufficiently sensitive. For this, measure 100 c.c. of the water 
into a clear bottle such as is used for the soap test, and add 2.5 
c.c. of the erythrosine indicator (0.1 gram of the sodium salt in 
one liter of distilled water), and five c.c. of chloroform neutral 
to erythrosine. Mix well by shaking and add N/50 sulphuric 
acid from a burette in small quantities, shaking thoroughly 
after each addition. The pink color in the water gradually 
grows lighter until the addition of a drop or two of the acid 
causes it to disappear entirely. Make a correction for the indi- 
cator by carrying out a blank determination with distilled water. 
Multiply the c.c. of acid used by 10 to get the alkalinity in terms 
of calcium carbonate. 

Procedure for Permanent Hardness. — Measure 200 c.c. of 
water into an Erlenmeyer flask, boil 10 minutes to expel carbon 
dioxide, and add 25 c.c. of N/10 soda reagent. For waters 
with a soap hardness over 300 use a 100 c.c. sample. Boil 
down to a volume of about 100 c.c, cool to 20 C, rinse into a 
200 c.c. calibrated flask with cooled, boiled distilled water, and 
make up to 200 c.c. Mix thoroughly. Filter through a dry 
filter paper, receiving the filtrate in a 100 c.c. calibrated flask. 
Discard the first 30 or 40 c.c, and then collect 100 c.c. of the 
filtrate. Pour into an Erlenmeyer flask, add one drop of methyl 
orange indicator and titrate with N/20 sulphuric acid. 

Make a blank determination with 200 c.c of distilled water 
in place of the sample. 

The difference between the amount of acid required by the 
blank and that required in the determination represents the 
amount of soda reagent used to precipitate the calcium and mag- 
nesium. To get the permanent hardness multiply this differ- 
ence by 25 when a 200 c.c. sample of water is used. 

If a water contains sodium or potassium carbonate, there will 
not be any permanent hardness, and hence more acid will be 



94 AIR, WATER, AND FOOD 

required for the nitrate than corresponds to the amount of 
soda reagent added. From this excess the amount of sodium 
carbonate in the water may be determined. Any alkali carbon- 
ate present would be calculated as temporary hardness by the 
direct titration; hence it should be calculated to calcium car- 
bonate and subtracted from the results found by the direct 
titration. 

Procedure for Total Hardness. — Boil down the neutralized 
sample obtained at the end of the alkalinity determination to 
about ioo c.c, add 25 c.c. soda reagent, again boil down to 100 
c.c, and proceed as in the determination of permanent hardness. 
The calculations are the same as described there. 

Free Carbonic Acid. — This determination depends on the 
reaction of sodium carbonate with carbon dioxide to form the 
bicarbonate, 

Na 2 C0 3 + H 2 + C0 2 -» 2 NaHC0 3 . 
As soon as all the free carbonic acid has been used up, the next 
drop of sodium carbonate will color phenolphthalein red. 

Reagents. — These are an N/22 sodium carbonate solution, 
and phenolphthalein indicator. 

Procedure. — Measure 100 c.c. of the sample into a tall, narrow 
vessel, preferably a 100 c.c. Nessler tube, add a few drops of 
phenolphthalein and titrate rapidly with N/22 sodium carbonate 
solution, stirring gently until a faint but permanent pink color 
is produced. 

The number of c.c. of N/22 sodium carbonate solution used 
in titrating 100 c.c. of water, multiplied by 10, gives the parts per 
million of free carbonic acid as C0 2 . 

Note. — Owing to the ease with which free carbonic acid escapes 
from water, particularly when present in considerable quantities, 
it is highly desirable that a special sample should be collected for 
this determination, which should preferably be made on the 
ground. If this cannot be done, approximate results from 
water not high in free carbonic acid may be obtained from 
samples collected in bottles which are completely filled so as to 
leave no air space under the stopper. 



WATER: ANALYTICAL METHODS 95 

Determination of Sulphates.* — Sulphates can be determined 
with an accuracy sufficient for most purposes by means of the 
Jackson Candle Turbidimeter.! The results are determined by 
the amount of turbidity produced by precipitated barium sul- 
phate. 

Procedure. — To about ioo c.c. of the water add sufficient 
dilute hydrochloric acid (about one c.c.) to acidify and then 
one-half a gram of barium chloride. Shake until dissolved. 
Pour slowly into the graduated tube of a candle turbidimeter 
until the image of the flame beneath just disappears. Read the 
height of the liquid in the turbidimeter tube and obtain from 
the table in Appendix A the parts per million of sulphates as S0 3 . 

Notes. — Care should be taken to have the solution well 
stirred before adding to the turbidimeter tube. The tube must 
not be placed over the flame when empty. Waters containing 
from 30 to 200 parts per million may be read directly; otherwise 
the water should either be concentrated or diluted. 

Determination of Alum. — On account of the use of alum or 
aluminum sulphate as a coagulant in the filtration of water, a 
determination of alumina in the effluent water is often neces- 
sary. This may be readily made by the logwood test.f 

Procedure. — The logwood solution is made as follows : Take 
two grams of logwood chips and boil one minute in a platinum 
dish with 50 c.c. of distilled water. Decant the solution and 
boil again for one minute with 50 c.c. of water. Decant this 
and similarly boil a third time with 50 c.c. of water. Decant 
this into a platinum receptacle for use. Take three drops for 
each test. Kept in platinum, the solution will last for several 
days at least. 

Test the water as follows: Boil 50 c.c. of the water in a plat- 
inum dish for a short time to expel carbon dioxide. Add three 

* "Laboratory Notes on Industrial Water Analysis," Ellen H. Richards, 1910. 
J. I. D. Hinds, /. Am. Chem. Soc, 18, 661 and 22, 269; D. D. Jackson, /. Am. 
Chem. Soc, 1901, p. 799; Muer, /. Ind. Eng. Chem., 1911, 3, p. 553. 

f For a description of this see references. 

% E. H. Richards, Tech. Quart., 1891, 4, p. 194; A. H. Low, Tech. Quart., 1902, 
15, P- 3Si. 



96 AIR, WATER, AND FOOD 

drops of the logwood solution and continue boiling for a few 
seconds to develop the color. Decant into a glass flask and 
cool quickly under the tap (so as not to keep the hot solution 
too long in the glass). Transfer to a No. 2 beaker and blow in 
carbon dioxide from the breath by means of a glass tube until 
there is no further decolorization. Pour the water into a Nessler 
tube for comparison with standards similarly prepared from a 
standard alum solution. Allow them to stand several hours 
before taking the final reading. No wash-water is used at any 
of the decantations. The test shows one part of aluminum 
sulphate in 8,000,000 parts of water. 

Notes. — A blank made with distilled water, if not completely 
decolorized by the C0 2 , will show a tint perceptibly fainter than 
that produced by one part in 8,000,000 of aluminum sulphate. 

It should be noted that carbon dioxide must be kept absent 
until the point prescribed. The solution is, therefore, transferred 
to a beaker in order to keep the flask free from carbon dioxide for 
the next test. 

The main points are: 

1. Any kind of logwood appears to answer. 

2. The solution is good for several days, at least, if kept in 
platinum. 

3. The use of platinum instead of glass for boiling the test 
solution. 

4. The use of carbon dioxide instead of acetic acid. 

Aluminum hydrate, as pointed out in 1893 by the late Profes- 
sor A. R. Leeds, will produce a tint almost as strong as if it 
were in solution, but of a distinctly differing tint. 

Low's method of procedure is as follows: First, test the 
water as above described. If no tint, or none exceeding that 
of the blank, remains after standing several hours or over night, 
that is sufficient. If, however, a tint persists, or a colored pre- 
cipitate settles out, it is necessary to determine if this is due to 
aluminum hydrate. Pour a sample of the water several times 
through a double Swedish filter, and finally test the filtrate. If 
the tint produced is weaker than that given by the unfiltered 



WATER: ANALYTICAL METHODS 97 

water, repeat the operation on a fresh portion of the water, 
using the same filter, and continue repeating with new portions 
of the water and always using the same filter, until it is apparent 
that no further diminution of the tint can be effected. 

For a less delicate test in school laboratories where platinum 
is not available, the following alternative method may be used: 

Dissolve about 0.1 gram pure haematoxylin in 25 c.c. water; 
this solution will keep for two weeks and works best after being 
made several hours. To 50 c.c. of the water, placed in a four- 
inch porcelain dish, add two drops of the haematoxylin solution, 
allow the solution to stand for one or two minutes, then add a 
drop of 20 per cent acetic acid. The standards are prepared at 
the same time, using 50 c.c. of distilled water and the required 
amount of a standard alum solution. The comparison must be 
made immediately, since the color fades on standing. In this 
way the presence of one part of aluminum sulphate in five mil- 
lion can be determined directly in the water and with ease. 

Logwood may be used instead of the haematoxylin, the solu- 
tion being prepared as above. 

This test will show the presence of all soluble salts of aluminum 
which enter into combination with the coloring matter of the 
logwood to form a "lake." 

The alkalies and alkaline earths give a purplish color with 
logwood extract, hence the test for alum can be made only in 
acid solution. 

Determination of Lead. — Lead in the minute quantities in 
which it ordinarily occurs in water is best estimated by comparing 
the color of the sulphide with standards. 

Procedure. — If the water is colorless, fill a 100 c.c. Nessler 
tube to the mark, acidify with a few drops of acetic acid, and 
add from a glass tube one drop of calcium sulphide solution. 
A black tint to the precipitated sulphur shows the presence of 
lead. A quantitative estimate may be made by comparison 
with a series of standards made from a standard lead solution. 

If the water is too highly colored to estimate the lead directly, 
evaporate three or four liters in a porcelain dish to about 25 c.c, 



98 AIR, WATER, AND FOOD 

add 10 ex. of ammonium chloride solution and a considerable 
excess of strong ammonia. Then add hydrogen sulphide water 
and allow the dish to stand some hours. Boil the contents of 
the dish for a few moments to expel the excess of hydrogen 
sulphide, and filter. The precipitate contains all the lead, iron, 
and suspended organic matter, also copper and zinc if present, 
while the soluble color goes into the filtrate. Wash once with 
hot water, transfer the filter to the original dish, and dissolve 
the sulphides by boiling with dilute nitric acid (1 part acid, 
sp. gr. 1.2, to 5 parts water). Filter and wash; evaporate to 
10-15 ex., cool, add 5 ex. concentrated sulphuric acid and evap- 
orate until copious fumes are given off. Then, if the original 
water contained less than 0.25 part iron per million, add acetic 
acid and ammonia, boil, filter and read the amount of lead in 
the alkaline filtrate, making the standards also alkaline with 
ammonia. 

If the water contained over 0.25 part iron, wash the lead 
sulphate into a beaker with alcohol and water, and let it settle 
overnight. Filter, wash free from iron with 50 per cent alcohol, 
dissolve the precipitate by boiling with ammonium acetate, 
filter, and determine the lead as above. 

Note. — If more than 0.25 part of iron is present, some of 
the lead will be held by the precipitated ferric hydroxide; and 
if 25 parts are present, all of the lead may be lost in this way; 
hence the modification of the method in the presence of consider- 
able quantities of iron.* 

When copper is also present it is detected by the blue color 
given to the ammoniacal filtrate from the iron precipitation. 

Determination of Phosphates, f — Procedure, — Evaporate 50 
ex. of the water and three ex. of nitric acid (sp. gr. 1.07) to 
dryness in a three-inch porcelain dish on the water-bath. Heat 
the residue in an oven for two hours at the temperature of boiling 
water. Treat the dry residue with 50 ex. of cold distilled water, 

* Ellms, J. Am. Chem. Soc, 1899, 21, p. 359. 

f Lepierre, Bull. Soc. Chim., 1896, 15, p. 1213; Woodman and Cayvan, /. Am. 
Chem. Soc, 1901, 23, p. 96; Woodman, ibid., 1902, 24, p. 735. 



WATER: ANALYTICAL METHODS 99 

added in several portions and poured into the comparison-tube. 
It is not necessary to filter the solution. Add four c.c. of ammo- 
nium molybdate (50 grams per liter) and two c.c. of nitric acid, 
mix the contents of the tube and compare the color, after three 
minutes, with standards made by diluting varying quantities 
of the standard phosphate solution (1 c.c. = 0.0001 gram P2O5) 
to 50 c.c. with distilled water and adding the reagents as above. 
Carry out a blank determination on the distilled water used for 
dilution, especially if it has stood for any length of time in glass 
vessels. 

Notes. — The method as described will be sufficient for ordi- 
nary work. If a more exact determination of the phosphate is 
required, a slight correction should be made in each case. For 
a table showing these corrections reference may be made to the 
paper by Woodman and Cayvan previously cited. 

The evaporation and heating with nitric acid is for the purpose 
of removing silica, which gives with ammonium molybdate a 
yellow color similar to that given by phosphates. 

The determination of phosphates in a drinking-water is a 
matter which has not received the attention from water analysts 
that has been given to the estimation of various other con- 
stituents. Any one who looks through the literature cannot 
help noticing how few are the published results of quantitative 
estimations of the phosphate content of natural waters, apart 
from mineral waters. Yet this determination, by reason of the 
conversion of organic phosphorus compounds into phosphates 
through the process of decay, is one which might reasonably 
be expected to throw considerable fight on the question of the 
pollution of natural waters by objectionable material. 

The reasons for this dearth of published data are not far to 
seek. To be of value the amount of phosphate must be known 
within rather narrow limits. Qualitative tests are not sufficient. 
The mere presence of phosphates is by no means definite or 
even confirmatory evidence of organic pollution. Rocks and 
minerals containing phosphates are found nearly everywhere, 
and traces, at times even considerable quantities, may be dis- 



IOO AIR, WATER, AND FOOD 

solved, especially by waters rich in carbonic acid. This, how- ' 
ever, does not constitute a serious objection to the utility of the 
determination. The same is true of many, if not most, of 
the constituents upon which reliance is placed in judging of the 
quality of a water. Unpolluted waters often contain notable 
amounts of nitrates and chlorides, and a true judgment can be 
rendered only after comparison with samples from adjacent 
but unpolluted sources. 

The chief reason, however, has been the lack of an accurate 
and simple method, sufficiently delicate, and of enough data 
to work out a standard for comparison. 

This reason can hardly hold true now, for enough work has been 
done on the colorimetric method to indicate its value as another 
link (of which we have none too many, anyway) in the chain of 
circumstantial evidence by which we are often compelled to 
judge the purity of a water. 

The amount of phosphate and its variation seem to follow 
the same general line as the other mineral constituents which 
either accompany the polluting material or are produced by its 
decay, especially the nitrates and chlorides. It is not, however, 
so delicate an indicator as these. In general, it may be said 
that the amount (expressed as P2O5) in an unpolluted water will 
seldom be over 1.0 part per million. 

Determination of Dissolved Oxygen. — Winkler Method* — 
The method depends on the absorption of oxygen by man- 
ganous hydroxide with the formation of manganese dioxide; 
the liberation of iodine by this last in an acid solution contain- 
ing potassium iodide; and the titration of the iodine with sodium 
thiosulphate. The reactions involved can be expressed as 
follows : 

MnS0 4 + 2 NaOH -> Mn (OH) 2 + Na 2 S0 4 . 

2 Mn(OH) 2 + 2 -> 2 Mn0 2 + 2 H 2 0. 

Mn0 2 + 2 H 2 S0 4 + 2 KI -> MnS0 4 + I 2 + K 2 S0 4 + 2 H 2 0. 

2 Na 2 S 2 3 + I 2 -> 2 Nal + Na 2 S 4 6 . 

* Berichte, 1888, 21, p. 2843; a l so see "Standard Methods of Water Analysis." 



WATER: ANALYTICAL METHODS 



IOI 



The method has recently been modified by Hale and Melia* 
by titrating the iodine in an acetic acid solution in order to 
avoid difficulties due to the presence of nitrites and nitrates, 
and this should be followed in testing for putrescibility. 

Collection of Samples. — The samples are collected in glass- 
stoppered bottles of known capacity, holding about 300 cubic 
centimeters. When water is taken from a faucet, the bottle 
is filled by means of a tube which passes to the bottom of the 
bottle. A considerable amount of water is allowed to pass 
through the bottle and overflow at the top. It will be almost 
impossible to obtain duplicate samples unless the bottles are 
filled at the same time by means of a T tube, owing to varia- 
tions in pressure in the pipes. 

In taking samples from a stream or pond, a stopper with two 
holes is used. A tube passing through one of these holes is 
sunk in the water to the desired depth, 
and the other is connected with a larger 
bottle of at least four times the capacity 
of the smaller one, and fitted in the same 
way. From the larger bottle the air is 
exhausted by the lungs or by an air-pump 
until it is nearly filled with water. Unless 
the determination is to be made at once, 
the rubber stopper of the smaller bottle is 
quickly replaced by the glass stopper so 
that no air is left in the bottle. The tem- 
perature of the water at the time of sam- 
pling should be noted. 

The apparatus which has been used in 
connection with work in this laboratory 
for collecting samples at various depths 
down to 75 feet is shown in outline in 
Fig. 10. A galvanized-iron can of such 
size as to hold one of the gallon bottles is weighted with 
lead and provided with ears at the top for suspending. The 

* /. bid. Eng. Ckem., 1913, 5, p. 976. 




Fig. 10. 



102 AIR, WATER, AND FOOD 

bottle, which is securely wired in, is provided with a rubber 
stopper carrying two brass tubes, one ending just below the 
stopper and projecting for about 8 or 9 inches above it, the 
other extending to the bottom of the bottle and connected by 
heavy rubber tubing with the sample bottle. This is held by 
brass brackets, which are fastened by means of a wooden cleat 
to the side of the can. The neck of the bottle is put into the 
slot in the upper bracket and then it is firmly clamped by the 
thumb-screw of the lower one. The arrangement of tubes in 
the sample bottle is obvious. In using the apparatus it is 
quickly lowered to the desired depth by means of a rope marked 
off in feet. The water enters the sample bottle and flows through 
it into the other. When the bubbles cease to rise, indicating 
that the larger bottle is full, thus replacing the water in the sam- 
ple bottle a number of times, the apparatus is drawn to the 
surface. The temperature is read from a thermometer fastened 
to the tube inside the gallon bottle. 

Reagents. — The reagents needed are solutions of man- 
ganous sulphate, potassium iodide in sodium hydroxide, potas- 
sium acetate, N/100 sodium thiosulphate, and starch indicator 
(see Appendix B). 

Procedure. — Remove the stopper from the 300-c.c. cali- 
brated bottle, and add two c.c. of manganous sulphate solution 
with a pipette having a long capillary point reaching to the 
bottom of the bottle, and in the same way add two c.c. of the 
solution of sodium hydroxide and potassium iodide. Insert 
the glass stopper, leaving no bubbles of air, and mix the contents 
of the bottle. Allow the precipitate to settle, remove the stopper 
and add two c.c. of concentrated hydrochloric acid from a 
pipette in the same manner as before. Replace the stopper, 
driving out some of the liquid, and shake until the precipitate 
is dissolved, and the liquid homogeneous. Remove 100 c.c. 
with a pipette or graduated flask, and titrate with N/100 sodium 
thiosulphate, using starch as an indicator. Add the starch 
solution, about two c.c, only after the iodine solution has be- 
come a light straw color. 



WATER: ANALYTICAL METHODS 



103 



To calculate the results proceed as follows: Let 7 equal the 
volume of the bottle with the stopper inserted and N the number 
of c.c. of thiosulphate used. One c.c. of N/100 sodium thio- 
sulphate is equivalent to 0.00008 gram of oxygen. The actual 
volume of water from which the oxygen was removed is equal 
to the volume of the bottle minus the four c.c. displaced by the 
first two reagents added. The liquid displaced by the acid does 
not need to be allowed for, as it did not contain any oxygen or 
iodine. The oxygen equivalent to the iodine titrated in the 
100 c.c. of the solution removed is equal to N X 0.00008. 

The oxygen equivalent to the total iodine liberated is equal to 

N X 0.00008 X 7 
100 

This is the oxygen present in the original water, which has a 
volume of (7 — 4), the four c.c. being the part displaced by the 
solutions added. The oxygen in parts per million is, therefore, 
equal to 

N X 0.00008 X 7 X 1,000,000 = 0.8 iVT 
100 X (7 - 4) 7 - 4 ' 

If the sodium thiosulphate solution is not exactly N/100, the 
correct oxygen equivalent should be substituted in place of the 

value 0.00008. 



QUANTITIES OF DISSOLVED OXYGEN IN PARTS PER MILLION 

BY WEIGHT IN WATER SATURATED WITH AIR AT THE 

TEMPERATURE GIVEN 



Temp. 

c. 


Oxygen. 


Temp. 

c. 


Oxygen. 


Temp. 
C. 


Oxygen. 


Temp. 

c. 


Oxygen. 


O 


14.70 


8 


11.86 


16 


9-94 


24 


8.51 


I 


14.28 


9 


11.58 


17 


9-75 


25 


8-35 


2 


13-88 


10 


II. 31 


18 


9-56 


26 


8.19 


3 


I3.50 


11 


II.05 


19 


9-37 


27 


8.03 


4 


13-14 


12 


IO.80 


20 


9.19 


28 


7.88 


5 


12.80 


13 


IO.57 


21 


9.01 


29 


7.74 


6 


12.47 


14 


10.35 


22 


8.84 


30 


7.60 


7 


12.16 


15 


10.14 


23 


8.67 







104 AIR, WATER, AND FOOD 

The results of this determination are frequently expressed in 
per cent of saturation, which is given by the ratio of the oxygen 
found to that present if the water were completely saturated 
at the same temperature. The latter figure is given by the 
preceding table. 

Procedure to be Followed in Putrescibility Tests or with Polluted 
Waters* — Follow the directions as given above until after the 
addition of the concentrated hydrochloric acid. Then replace 
the stopper and shake until all the precipitate is dissolved. 
Remove the stopper and add from a pipette two c.c. of potassium 
acetate solution. Mix by pouring into a flask or beaker and 
back into the bottle. Remove ioo c.c. as before and titrate 
with N/ioo sodium thiosulphate. 

The addition of the acetate increases the volume of the iodine 
solution from V (the volume of the bottle) to (V + 2), and this 
should be substituted in the formula given on p. 103. The oxygen 
in parts per million will, therefore, be equal to 

0.8 N (V + 2) 
V-4 

Notes. — If water is collected in the ordinary way and trans- 
ferred to the apparatus by pouring, there will inevitably be 
an absorption of oxygen unless the water is already saturated. 
Thus a process which gives excellent results when the water is 
nearly or quite saturated may fail entirely to give accurate 
results when the dissolved oxygen is low or absent. The water 
may be supersaturated with oxygen in which case the per cent 
of saturation may be more than ioo.f 

Determinations of dissolved oxygen in ponds and streams are 
best made on the spot, or, at least, the reagents should be added 
until after the addition of the hydrochloric acid. The very 
simple apparatus required for the Winkler process can be packed 
in a small space, and the entire determination requires only a 
few minutes. The absorption of the oxygen by the manganous 

* See article by Hale and Melia, loc. cit. 
t Gill, Tech. Quart., 1892, 5, p. 250. 



ongressional Reading Room 







•2 f|p£ 



r ;-tf**-t * 



raooH snibssfl IfinoieeaTgfK 



"vT 



WATER: ANALYTICAL METHODS 105 

hydroxide is complete almost at once, and it is unnecessary to 
allow it to settle for a long time before adding the acid. The 
titration can be made with a small burette or pipette with 
accurate results. 

Putrescibility Test.* — There is at the present time no really 
satisfactory standard putrescibility test. One which seems to 
have been worked out on logical principles and which has given 
satisfaction in this laboratory is that proposed by the Royal 
Sewage Commission. The putrescibility is measured by the 
absorption of dissolved oxygen under given conditions. A 
stream water or diluted sewage or effluent, — the water used 
for dilution furnishing the necessary oxygen, — is tested for 
dissolved oxygen. A sample is then incubated in a closed bottle 
for five days at 20 C. and the dissolved oxygen again deter- 
mined. The difference represents the oxygen absorbed, and 
should not be greater than 20 parts per million. 

Procedure. — If the water is from a stream or lake, fill com- 
pletely two 300-c.c. calibrated glass-stoppered bottles. Insert 
the stoppers, taking care that no air bubbles are enclosed. If a 
sewage or effluent is being tested, make dilutions with tap water 
as follows: 

Raw sewage. Dilute 6 c.c. to 600 c.c. 
Settling tank effluents. Dilute 12 c.c. to 600 c.c. 
Filter effluents. Dilute 120 c.c. to 600 c.c. 
Fill two calibrated bottles as just described. 

Make a dissolved oxygen test on one bottle, following the 
directions as given for putrescibility tests. Set the other bottle 
in a 20 incubator and let stand for five days. Then determine 
the dissolved oxygen again. Calculate the results in terms of 
oxygen absorbed by the original sample of water, sewage or 
effluent. 

Determination of the Color. — The amount of color is gen- 
erally determined by direct comparison of the water with some 
definite standard of color. Various standards have been pro- 

* Eng. Rec, 1913, 68, pp. 315 and 453; Am. J. Pub. Health, 1914, 4, p. 241. 



106 AIR, WATER, AND FOOD 

posed, the objection to most of them being that they are not 
sufficiently general in their application, being adapted only for 
the color of some particular class of waters. 

The standard in most general use is the platinum standard. 
The comparisons of the water with the color standards are most 
readily made in 50-c.c. Nessler tubes. According to this scale, 
the color of a water is the amount of platinum in parts per 
million, which, together with enough cobalt to match the tint, 
must be dissolved in distilled water to produce an equal color. 
In practice, a standard having a color of 500 is prepared by dis- 
solving 1.246 grams of potassium platinic chloride (equivalent 
to 0.5 gram platinum), 1.0 gram of cobalt chloride (equivalent 
to 0.25 gram cobalt), and 100 c.c. of strong hydrochloric acid in 
distilled water and diluting to one liter. 

Dilute standards for use are made by diluting varying amounts 
of this standard to 50 c.c. with distilled water. Thus, by dilut- 
ing one c.c, two c.c, and three c.c. each to 50 c.c, colors of 10, 
20, and 30 are obtained. It is claimed that the platinum 
standards are permanent if protected from the dust, but in this 
laboratory it has been found necessary to replace them about 
once a month. 

Determination of the Odor. — Cold. — Shake violently the 
sample in one of the large collecting-bottles when it is about 
half or two-thirds full, then remove the stopper and quickly 
put the nose to the mouth of the bottle. Note the character 
and degree of intensity of the odor, if any. An odor can be often 
detected in this way which would be entirely inappreciable if 
the water were poured into a tumbler. 

Hot. — Pour into a plain beaker about five inches high enough 
water to one-third fill it. Cover the beaker with a well-fitting 
watch-glass and place it on an iron plate which has been pre- 
viously heated, so that the water shall quickly come to a boil. 
When the air bubbles have all been driven off and the water is 
about to boil, take the beaker from the plate and allow it to cool 
for about five minutes. Then shake it with a rotary movement, 
slip the watch-glass to one side and put the nose into the beaker. 



WATER: ANALYTICAL METHODS 107 

Note the odor as before. The odor may or may not be the same 
as that of the water when cold; it can be perceived, as a rule, 
for only an instant. 

Notes. — It is inevitable that a certain personal equation 
should influence this test. Each laboratory will have its own 
standards for routine work, but a certain familiarity with the 
more common odors will tend to allay public anxiety and to aid 
in a more watchful habit on the part of consumers. Good 
ground waters do not give distinct odors unless they are derived 
from clayey soil, but the odor often betrays a contaminated 
well. Surface-waters will nearly always yield a characteristic 
odor. This odor may be due to the organic matter contained 
in the water, or to the presence of minute plants or animal 
organisms. 

Among the odors which are frequently met are "earthy,'' 
"vegetable," "musty," "mouldy," "disagreeable," and "offen- 
sive." The "earthy" odor is that of freshly turned clayey soil. 
"Vegetable" is the odor of many normal colored surface-waters; 
it may be described as swampy or marshy, pond-like, and is 
often strengthened by heating. "Musty" can be likened to 
the odor of damp straw from stables; it is fairly characteristic 
of sewage contamination, and by the trained observer is dis- 
tinctly distinguishable from the mouldy odor. "Mouldy" is 
the odor of upturned garden or forest mould, or of a moist hot- 
house; it is somewhat allied to the earthy odor. "Disagree- 
able " is a term which is capable of wide variation among different 
observers. It may include certain characteristic odors which 
are peculiar to the growth or decay of certain organisms, as the 
"pigpen" odor of Anabcena, the "fishy" or "cucumber" odor 
of Synura, etc. The term "offensive" is generally reserved for 
the sewages. These terms can be taken only as broad illustra- 
tions of the character of the particular odor, since the odor will 
very likely be described by different persons in different ways, 
and each laboratory will have its own characterization. The 
odor which often accompanies an abundant development of 
diatoms is a good illustration of this. It will be called by various 



108 AIR, WATER, AND FOOD 

inexperienced observers offensive, rotten, fishy, geranium-like, 
aromatic, in one and the same sample of water. 

The terms generally used to signify the degree of intensity 
of the odor are "very faint," "faint," "distinct," and "decided." 
The exact value to be placed upon each of these terms will, as a 
matter of course, vary with the individual analyst, but in a 
general way, it may be said that the "very faint" odor is one 
that would not be detected except by the trained observer; the 
"faint" odor would be recognized by the ordinary consumer if 
his attention were called to it; the "distinct" odor is one that 
would be readily noticed by the average consumer, but would 
not interfere with the use of the water; while the "decided" 
odor is one which would, in all probability, render the use of 
the water unpleasant. 

Determination of the Turbidity and Sediment. — The sus- 
pended matter remaining in the water after it has rested quietly 
in the collecting-bottle for twelve hours, or more, is called its 
turbidity, and that which has settled to the bottom of the bottle, 
its sediment. 

Good ground waters are often entirely free from turbidity 
and sediment, the suspended matters having been filtered out 
during the subterranean passage of the water, but this is rarely 
true of surface-waters. The turbidity is various in character 
and amount, sometimes milky from clay or ferrous iron in solu- 
tion; usually it consists of fine particles, generally living algae or 
infusoria. These often collect on the side toward or from the 
light, and a practiced eye can, not infrequently, recognize their 
forms. Some of the lower animal forms can also be seen by the 
naked eye, and the larger Entomostraca are quite noticeable 
in many waters. 

The sediment may be earthy or flocculent; in the latter case 
it is generally debris of organic matter of various kinds. The 
degree of turbidity is expressed by the terms "very slight," 
"slight," "distinct," and "decided," and the degree of sedi- 
ment by "very slight," "slight," "considerable," and "heavy." 
These determinations, again, are of value only to the routine 



WATER: ANALYTICAL METHODS 109 

worker, and for him there are various methods in use. The 
papers of Parmelee and Ellms * and of Whipple and Jackson f 
should be consulted for a description of these. 

Sewage Analysis. J — The methods for the analysis of sew- 
ages and sewage effluents are the same as those described for 
water. The main difference is in the quantities used for the 
various determinations. In most cases, this has been noted in 
connection with the analysis. Great care should also be exer- 
cised in taking samples from a bottle as the large amount of 
suspended matter makes it more difficult to obtain a represent- 
ative portion. Special attention is called to the putrescibility 
test (p. 105) for effluents, as stability is the main desire in treat- 
ing a large proportion of sewages. 

Biological Examination. — Since a large number of, if not all, 
diseases are caused by living organisms, it would seem most 
desirable in examining a water supply if the specific organisms 
causing water-borne diseases could be looked for, and, if present, 
isolated. However, it is quite impossible to do this in the great 
majority of cases, and so in bacteriological work, just as in 
chemical analysis, certain indications of the presence of sewage 
are sought for, and if these indications are positive, the water 
is condemned. In a bacteriological examination, the most 
important index of the presence of sewage is rinding B. coli in 
quantities as great as one in each cubic centimeter. This 
organism is a normal inhabitant of the intestines of man and 
the higher animals and is present in large numbers in human 
and animal excreta. Its presence, therefore, in water shows 
the presence also of sewage. For a discussion of water bacteri- 
ology and methods of analysis the reader is referred to another 
book.§ 

The close relation of the odor to the living flora and fauna of 

* Tech. Quart., 12, 1899, p. 145. 
t Ibid., p. 283. 

X See Fowler "Sewage Works Analyses," John Wiley & Sons, 1902. 
§ Prescott and Winslow, "Elements of Water Bacteriology," 3rd edition, 
John Wiley & Sons, 19 13. 



HO AIR, WATER, AND FOOD 

the water makes it desirable that the chemist shall be able to 
recognize the more common forms of water plants and animals, 
even if he make no pretensions to a knowledge of cryptogamic 
botany or of zoology. Therefore, a microscope and a concen- 
tration apparatus should be in every water-laboratory. A full 
description will be found elsewhere.* 

* Whipple, "The Microscopy of Drinking Water," 3rd edition, John Wiley 
& Sons, 19 14. 



CHAPTER VII 

FOOD IN RELATION TO HUMAN LIFE: COMPOSITION, 
SOURCES, DIETARIES 

Life itself is conditioned on the food-supply. Wholesome 
food is a necessity for productive life. Man can and does exist 
on very unsuitable, even more or less poisonous, food, but it is 
merely existence and not effective life. This is true not only of 
the wage-earner, but of the business-man, the professional man, 
the scholar. To be well, to be able to do a day's work, is man's 
birthright. Nevertheless, a too large proportion of the American 
people sells this most valuable possession for a mess of pottage 
which pleases the palate for three minutes and weights the diges- 
tive organs for three hours. With the products of the world ex- 
posed in our markets, the restraints of a restricted choice, as well 
as inherited instincts or traditions, lose their force. The buyer, 
unless he has actual knowledge to guide him, is swayed by the 
caprices of the moment or the condition of his purse, and often 
fails to secure adequate return in nutritive value for the money 
paid. The fact that so much manipulated material is put upon 
the market renders this choice of food doubly difficult, since the 
appearance of the original article is often entirely lost, and to 
city-bred buyers even the natural product conveys little idea of 
its money value. It is now even more necessary that an elemen- 
tary knowledge of the proximate composition and food value of 
the more common edible substances should be recognized as an 
essential part of education. 

Food: Definition and Uses. — Food is that which builds up the 
body and furnishes energy for its activities: that which brings 
within reach of the living cells which form the tissues the elements 
which they need for life and growth. Only such available sub- 
stances can be called food, no matter what their chemical compo- 



112 AIR, WATER, AND FOOD 

sition may be. Soft coal contains carbon and hydrogen and is 
food for the furnace, but is not available for the animal body. 

This food which is taken into the body is used in various ways. 
It forms and builds up new tissues, besides repairing and making 
good the waste of tissues due to bodily activity; it is stored up in 
the body to meet a future demand; it supplies the needed heat 
by the transformation of its stored up or potential energy into 
the muscular energy required by the body; it may be used to 
protect the tissues of the body from being themselves consumed 
as food. 

Composition of Food. — We determine what chemical elements 
enter into the composition of the body by an analysis of the vari- 
ous organs and tissues. We learn what combinations of these ele- 
ments serve as food by determining those present in mother's milk 
and in foodstuffs which experience has proved to furnish perfect 
nutrition. From these studies it is apparent that about fifteen 
chemical elements are constant constituents of the human body; 
that about a thousand natural products are known to have food 
value; that of these, one hundred are of world-wide importance 
(see table, page 118), and that ten of them form nine- tenths of 
the food of the world. 

The composition of food, as shown by chemical analysis, is 
not, however, the only factor that must be known to determine its 
value. The digestibility of the material must be taken into ac- 
count as well. "We live not upon what we eat, but upon what 
we digest." It is more important to know the amount of availa- 
ble nutrients than the amount of total nutrients. 

Food Principles. — While the foodstuffs present great variety, 
the food principles may be grouped under four headings; viz., 
nitrogenous substances or proteids, fats, carbohydrates, and 
mineral salts. Each group contains many members with minor 
but often essential differences. To make these substances 
available, there is needed an ample supply of air and of water, 
— of water for solution and circulation, of air for the oxygen 
needed to liberate the stored energy of the food in the place 
where it will accomplish its purpose. 



FOOD IN RELATION TO HUMAN LIFE 1 13 

Nitrogenous Substances. — Since, in some way as yet un- 
known to us, nitrogen is essential to living matter, such sub- 
stances as contain this element in an available form are of the 
first importance. Some, as albumen, are so closely allied to 
human protoplasm that probably they need only to be dissolved 
to be at once assimilated. Others, as gluten and similar vege- 
table products, undergo a greater change; while still others, 
as gelatine, have a less profound but marked effect in protecting 
the tissues from waste. 

The' enzymes, " ferments," in part, of the older nomencla- 
ture, are also highly nitrogenous substances present in some 
form in nearly all foodstuffs of natural origin. The nearer the 
composition of the food approaches that of the protoplasmic 
proteid, presumably' the greater its food value, since each cleav- 
age, each hydrolysis, each step in the breaking down of the 
highly complex molecule, consisting of hundreds of atoms, is 
supposed to liberate the stored energy. Therefore, it is not a 
matter of indifference in what form this essential is taken. So 
little is known, however, with scientific accuracy that students 
will find a fruitful field of research along these lines of inves- 
tigation. Also together with this element, nitrogen, go others, 
in small quantity to be sure, but evidently of great value. Such 
are sulphur, iron, phosphorus. One difference between the 
several groups of proteids is seen in this combination with the 
metallic elements which seems to carry with it certain effects. 
Until greater progress has been made in determining the 
availability in the organism of the various known substances, 
we must be content with a wide margin in the calculated quan- 
tities necessary for the daily efficiency, except in the very few 
instances of nearly pure substances, as white of egg. It is 
evident, also, that the manner of preparation and the kind of 
mixtures used in food will affect most profoundly so unstable 
and complex a class of substances. One thing is certain, that 
the body cannot take nitrogen from that which does not contain 
it. Therefore, a certain quantity of highly nitrogenous food 
should form a portion of the daily supply. It is usually held 



114 AIR, WATER, AND FOOD 

that the body seems to be sufficiently nourished when the food 
contains an amount of digestible proteid equivalent to about ioo 
grams of dry albumen per day for the average adult, although 
recent work has shown that this figure is probably too high. 
An excess appears to have a stimulating effect and overloads 
the system with the waste, since the end-products are not purely 
mineralized substances, as are carbon dioxide and water from 
the carbohydrates, but are compounds of an organic nature, 
as creatin, urea, and uric acid, which have deleterious effects 
when accumulated in the system. A deficiency of nitrogen is 
made good, to a limited extent, by the protective agency of the 
other foodstuffs which offer themselves for all the offices except 
the final one of tissue-building. 

Fats. — For this protective action, as well as for many other 
purposes, the fats are most valuable, and if they occur in about 
the same proportion as do the nitrogenous elements, the needs 
of the organism seem to be well met. Thus, in mother's milk, 
in eggs, and in meat from active animals these two are in nearly 
equal proportions, while in the cereals the fat is less; in nuts 
and in meat from fattened animals, as a rule, it is higher than 
the nitrogen. Little is known as to the varying food value of 
these fats from different sources. Certain physical conditions 
of solidity, melting-point, etc., seem to have more influence 
than mere chemical composition. Whatever the source, it is 
certain that the stored-up energy which is to serve the organism 
in cases of loss of income from any cause is in the form of fat, 
a form which is not subject to the action of agents which so 
readily decompose proteids and carbohydrates and yet is readily 
converted into available food whenever called for. That it is 
not absolutely necessary that the food should contain fat as 
such seems to be proved by experiment, but from the fact that 
nearly all natural food-substances do contain it, and that it 
appears to be more economical of human energy to take it from 
these foods than to manufacture it from the proteids and carbo- 
hydrates, we may safely assume fat to be an essential of the 
human dietary. 



FOOD IN RELATION TO HUMAN LIFE 115 

That the equality in amount of fat with nitrogenous com- 
pounds is not essential is proved by the fact that the strong 
draft animals, as horses and oxen, take food in which the per 
cent of fat is not more than half as much as of proteid; never- 
theless, it is present in the food of all animals and doubtless, 
in its turn, is protected by an excess of the third class of food- 
stuffs, the carbohydrates, characteristic of the vegetable king- 
dom — a class which in the final decomposition, yields clean 
volatile products, water and carbon dioxide, and which, there- 
fore, do not clog the system so readily as do urea and other 
wastes. 

Carbohydrates. — The number of more or less well-defined 
substances under this head is legion: starches from scores of 
plants, sugars from as many more, gums, pectins, and dextrins, 
all with a certain food value, dependent probably upon the 
utilization of the various mixtures with which they are taken 
into the alimentary canal. These foodstuffs are very liable to 
''fermentation," that is, to an acid decomposition which pre- 
vents their absorption by the delicate lining of the walls of the 
intestines and which causes digestive disturbance. The sugars, 
which are very soluble, and, therefore, liable to be present in 
excess, are especially subject to this change. This class of 
food-substances is found in the diet of civilized man, free to 
choose, in an amount about equal to the sum of the other two 
classes, with a tendency to less rather than mere. It may be 
said that sugar and fat increase over starch in the diet of a people 
of unrestricted choice, but it is not certain that the qualities of 
body which make for hardihood and resistance to disease are 
correspondingly increased. There is, indeed, much evidence 
to show that power of digesting vegetable foods indicates a 
general well-being of body conducive to long life. A ready 
adaptation renders possible the changes of habitat required by 
civilization. Unless one is to be confined to a narrow range, it 
is wise to cultivate a strength of digestion as well as a strength of 
muscle, and for the best brain power we believe it to be more 
essential. 



Il6 AIR, WATER, AND FOOD 

Mineral Salts. — The fourth class, mineral salts, comes into 
the food largely from the vegetable substances eaten, for in 
these the union is an organic one readily assimilated. As we 
have seen, certain elements go with the nitrogenous portion, 
as, for example, in gluten and its congeners are found sulphur 
and phosphorus. Potassium, found in barley, is a constant 
constituent of protoplasm, while sodium is found in blood- 
serum. A lack of vegetable foods seems to impoverish the 
blood-corpuscles. For children, a deficiency in lime causes 
serious disease. Sugar, olive-oil, corn-starch and other prepared 
food-substances cannot take the place of asparagus, cabbage, 
carrots, etc. 

To sum up briefly, then, we may say that the protein or nitrog- 
enous portion of the food forms tissue, such as muscle, sinew and 
fat, and furnishes energy in the form of heat and muscular 
strength; the fats build up fatty tissue, but not muscle, and 
supply heat; the carbohydrates are changed into fat and supply 
heat. Another important use of the nutrients is to protect 
each other from being used in the body. The carbohydrates, 
especially, in this way protect the protein, including muscle, 
etc., from consumption. 

Change in Composition Due to Cooking. — The composition of 
cooked foods is in general not the same as the raw material on ac- 
count principally of chemical and physical changes brought about 
by the heat employed in the cooking process. The total nutri- 
ents, calculated on a water-free basis, may be practically the 
same, but the structure is often quite different. 

Starch is hydrolyzed and rendered soluble by heating in the 
presence of moisture, and at higher temperatures it may be 
converted into the brown, soluble dextrin. The sugars are 
changed, being, in the case of sucrose, partly converted into 
other forms, such as invert sugar, by the heating, with the help 
of the organic acids present in many foods. Some of the proteids 
tend to become less soluble through heating and at higher tem- 
peratures may be even partly decomposed with possible loss of 
food value. 



FOOD IN RELATION TO HUMAN LIFE 1 17 

Heat of Combustion. — Until a more definite knowledge of the 
processes of metabolism (the transformations of matter and 
energy in the animal organism) is obtained the potential energy 
of food is calculated in terms of mechanical work — expressed 
in heat-units or calories. 

One calorie is the amount of heat required to raise the tempera- 
ture of one gram of water one degree centigrade. A gram of fat, 
as actually digested and oxidized in the body, affords enough 
heat to raise the temperature of about 9000 grams of water one 
degree. In like manner a gram of protein has an energy-pro- 
ducing power expressed in calories of about 4000, and for carbo- 
hydrates the average value is also 4000. 

Allowance is made in these figures for the fact that to digest 
completely any part of our food results in a decrease of the 
amount of energy to be derived from it, and this affects the 
protein more than it does the other two. It is probably true 
that under favorable conditions the fat and carbohydrates 
can be completely utilized in the body and consequently their 
energy-producing power can be correctly estimated from their 
heat-producing power outside the body. In the case of pro- 
tein, however, the digestion within the body is never so com- 
plete as to furnish all the energy that would be obtained by a 
complete combustion of these nitrogenous materials outside of 
the body. 

The fact remains, however, that all experiments yet made go 
to show that within practical limits we are safe in using the heat 
of combustion (expressed in calories) of any food-substance as a 
controlling measure of food values. 

Nutritive Ratio. — The requisite number of calories must, how- 
ever, be obtained by the utilization of such substances as contain 
all the elements needed by the body, and in such ratio as has been 
found available for the balance of nutrition. In carrying on its 
multifarious activities the body loses about 20 grams of nitrogen 
per day, which must be replaced by the same element in the food 
taken. Thus while the requisite number of calories may be fur- 
nished by fat or starch, these substances alone will not suffice for 



n8 



AIR, WATER, AND FOOD 



COMPOSITION OF SOME COMMON FOOD-MATERIALS AS PURCHASED 

I. Fuel Value 3000-4000 Calories * per Pound 



Food-material. 


Refuse. 


Water. 


Nitroge- 
nous 
Substances 


Fat. 


Carbo- 
hydrates. 


Butter 


Per cent. 


Per cent. 
11. 


Per cent. 

1.0 


Per cent. 

85.0 

100 . 00 

83.0 

80.3 to 94.1 

70.7 to 94.5 

63.4 


Per cent. 












9-5 
0.3 to 12.2 
4.3 to 21.9 

2.5 


1.2 

0.2 to 5.0 

1.1 to7-5 

16.6 










Suet 






Walnuts (shelled) 




16. 1 



II. Fuel Value 2000-3000 Calories per Pound 



Bacon 

Cheese (American pale). 

Chocolate 

Doughnuts 

Mutton flank (fat) 

Peanut butter 

Sausage (farmer) 



Barley (pearled) 

Beans (dried) 

Cake average (except fruit ) . . 

Candy 

Cheese (Neuchatel) 

Corn meal 

Corn-starch 

Crackers (average) 

Fat meats 

Gelatin 

Ham (smoked, medium fat). 
Infants' and invalids' foods. 

Macaroni 

Oats 

Peanuts 

Peas (dried) 

Pop-corn 

Rice 

Rye flour 

Sugar (granulated) 

Wheat (entire) flour 

Wheat flour (white bakers'). 

Wheat (shredded) 

Zwieback 




18.4 

316 

1.5 to 10.3 

11. o to 25.8 

28.9 

2.1 
22.2 



9-5 
28.8 


59.4 
359 


03 


12.5 to 13.4 


47- 1 to S0.2 


26.8 to 33.8 


S.i to 7-6 


16.4 to 25.7 


45.8 to 63.2 


10.7 


59-8 




29-3 


46.5 


17. 1 


27.9 


40.4 





III. Fuel Value 1500-2000 Calories per Pound 



11. 7 

4.5 to 28. 



245 



9.8 to 12.9 

9.6to 15.5 

19.9 

4.0 

42.7 to 57-2 

8.8 to 17.9 
10. o 

6.8 

38.3 

136 

27.3 to 42.5 

2.4 to 12.3 

7.0 to 12.3 

7.8 
6.9 

6.9 to 15.0 
4-3 

9.1 to 14.0 
11. 9 to 136 



6.4 to 13. 1 
10. 1 to 133 

7.2 to 10.7 
S.o to 7-7 
Including fibre 



7.0 to 10. 1 

19.9 to 26.6 

6.3 

15. 1 to 22.3 
6.7 to 11. 6 

10.7 
130 
84.2 

10.2 to 21.9 
2 . o to 22 . 5 
7.9 to 16.6 

16.5 

195 

20.4 to 28.0 

10.7 

5-9 to 11. 3 
4-9to 8.8 

12.2 to 14.6 

10.3 to 14.9 
9.6 to 11. 4 
8.6 to 11. 7 



0.7 to 1.5 


1.4 to 3.1 


9.0 


22.3 to 32.5 


1.0 to5.3 


8.8 


36.8 


0.1 


245 to 39-9 


0.3 to 10.9 


0.0 to 4.9 


7-3 


29.1 


0.8 to 1.3 


5.o 


0.1 to 0.7 


0.2 to 1.3 


1.5 to 2.1 


1.9 tO 2.0 


1.3 to 1.6 


8.1 to 11. 3 



IV. Fuel Value 1000-15000 Calories per Pound 



Apples (dried) 

Bread (white) 

Corn-bread 

Dates 

Figs 

Fresh pork (ribs and shoulder) . 
Medium fat mutton and beef. . 

Mince-meat (commercial) 

Mince-meat (home-made) 

Pies 

Prunes (dried) 

Raisins 

Sandwiches 

Sardines (canned) 

Salt mackerel 



15.9 to 20.3 
14.4 to 27.8 



150 
10. o 



8.6 tc 


47-4 


35-3 


28.4 to 48.0 


13.8 


11. 6 to 25.0 


40.1 to 43-6 


38.0 to 44-9 


27.7 


54 


4 


44 


9 


19 





13 


I 


44 


9 


53 


6 


32 


5 



1 . 2 to 2 . 5 

92 
6.5 to 10. 1 

1-9 

2.6tO 5-7 

13.7 to 14.5 
11. 4 to 12.9 

6.7 

4-8 

4-4 

1.8 

2.3 
10.9 
237 
16.3 




77-3 to 78.1* 
57-2 to 63.5* 

633 

96.0 
0.2 to 2.9 
68.4 to 80.6* 

90.0* 

71.9* 



66 . 9 to 89 . 4 

67.2 to 78.4* 
66.5* 
18.5 

58.0 to 67.4* 

78.7 
75-4 to 81.9* 
77.6 to 80.2* 

100 

69.5 to 770* 

70.3 to 755 

75.0 to 79-7* 

72.1 to 74-2 



48.6 to 86.91 

53- 1 
40.3 to 54-3 

70.6 
68.3 to 83.1 



60.2 
32.1 

39-2 
62.2 
68.5 
33-3 



* One Calorie equals iooo calories. 



FOOD IN RELATION TO HUMAN LIFE 



119 



COMPOSITION OF SOME COMMON FOOD MATERIALS. — Continued 

V. Fuel Value 500-1000 Calories per Pound 



Food-material. 


Refuse. 


Water. 


Nitroge- 
nous 
Substances 


Fat. 


Carbo- 
hydrates. 




Per cent. 

8.5 

12.8 

18.0 to 42.7 


Per cent. 
62.5 
540 

38.3 to 53-7 
74.o 
65.5 
19.2 

59.9 to 69.2 

52.4 

45.oto 51.2 
54-6 to 58.2 

52.0 to 71.6 

32.4 to 69.2 

41. 1 to 44-7 

48.5 to 55-7 


Per cent. 
19.2 
16. s 

11. 5 to 16.0 
2.5 

11. 9 
20.5 

18. 1 to 21.4 
1-4 

12.6 to 15.0 
18.6 to 20.2 

2.8 to 4.2 
7 . 8 to 20 . 2 
15.8 to 16.8 

14.2 to 16.9 


Per cent 
9-2 
16. 1 
6.9 to 21.5 
18.5 
93 
8.8 

7.8 to 14.2 
21.0 

6.6 to 9.5 
5.6 to 98 

2.3 to 4.8 
0.7 to 15.3 

5.9 to 25.5 

9.4 to 12.8 


Per cent. 














Eggs 


11. 2 

444 
0.5 to 11. 3 

19.0 
23-8 to 35-1 
11. 7 to 16.9 












Olives 


35 


Salmon (canned) 










9.2 to 55-3 
17. 1 to 32.4 
15.7 to 25.4 








Veal (breast) 





VI. Fuel Value 400-500 Calories per Pound 



Beans (canned red kidney) , 

Calf's-foot jelly. . . 

Salt cod (boneless) 

Succotash (canned) 

Sweet potatoes 



1.6 



72.7 


77.6 


54.8 


71.4 to 79-9 


55.2 



7.0 
4.3 
27.7 

2.9 to 4.4 
1-4 



0.7 to 1.7 
0.6 



VII. Fuel Value 300-400 Calories per Pound 



Bananas 

Butter beans. 
Fish (fresh).. 

Grapes 

Hash 

Milk 

Potatoes 



3S.o 

50.0 

25.2 to 46.0 

25.0 



48.9 

29-4 

46.1 to 49.1 

58.0 
80.3 
87.0 
62.6 



0.8 
4-7 
11. 9 to 12. 
1.0 

6.0 
3.3 

1.8 



0.4 
0.3 
1.8 to5-9 
1.2 
1.9 
4.0 



VIII. Fuel Value 200-300 Calories per Pound 



Apples 


25.0 














Oysters (solid) 








Pears 


10. 



63.3 

44-6 to 52.4 
87.6 to 89.5 

78.9 
82.2 to 92.4 

66.4 

76.2 



0.3 
9.0 to 15.7 
0.4 to 0.5 

1.4 

4-5 to 7.3 

1.3 

0.5 



0.3 

1.1 to 1.8 

0.4 to 0.9 

0.3 

0.5 to 1.8 

0.4 
0.4 



18.5 
17-4 



14.9 to 22.4 
21.9 



143 
14.6 



14.4 
9-4 

5-0 
147 



10.8 



9-3 to 10.9 

8.9 
1.5 to 6.2 
10.8 
12.7 



IX. Fuel Value 100-200 Calories per Pound 



Beets 


20.0 
15.0 
20.0 
61.0 
30.0 
27.0 






Green corn 








Spinach 




Squash 


50.0 


Tomatoes (canned) 



70.0 

77.7 
70.6 
29.4 

62. 5 
634 

91.0 to 92.8 
91.6 to 92.8 

44-2 
92.5 to 97-9 



1.3 

1.4 
0.9 

1.2 
0.7 
0.6 

2.9 to 5.0 
1.8 to 2.4 

0.7 
0.3 to 1.7 



0.1 

0.2 

0.2 

0.4 

0.5 

0.1 
0.2 to 0.8 
0.2 to 0.5 



X. Fuel Value io-ioo Calories per Pound 



Asparagus 

Bouillon (canned). 

Celery 

Cucumbers 

Watermelons 



20.0 
15.0 
59-4 



94.0 
96.5 to 96.7 
75-6 
81. 1 
37-5 



1.8 
1.7 to 2.6 
09 
0.7 
0.2 



0.2 

0.0 tO 0.2 
O.I 
0.2 
O.I 



7-7 
4-8 
7-4 
7-7 
59 
8.5 

0.6 to57 
3-1 to34 

4-5 
1.4 to 8.1 



33 
0.1 to 0.3 

2.6 
2.6 

2.7 



120 AIR, WATER, AND FOOD 

complete nutrition. The nutritive ratio, or the proportion of 
nitrogenous to non-nitrogenous food, must be maintained in the 
proportion of i to 3, or at least 1 to 5. 

The preceding table of one hundred common food-materials 
is arranged in the order of calorific or energy-giving power, but 
in considering the food value of any one substance its nitro- 
gen content must also be considered, and such combinations 
made as will yield the requisite elements for a well-balanced 
ration. 

From even a cursory examination of the table it will be seen 
how widely some of the foodstuffs differ under differing con- 
ditions of soil moisture, fertilization in the case of plants, and 
of fatness or leanness in animals, of method of preparation or of 
combination in cooked foods. 

Therefore examinations of materials are imperative if there is 
to be any basis of calculation. In an institution where, for 
instance, flour forms two-thirds of the daily ration, if it con- 
tains the lowest per cent of nitrogen it may not furnish sufficient 
proteid for a well-balanced ration, or if the meat used is very 
lean there may not be fat enough for the best nutrition. 

The great variation in the proportion of water leads to many 
surprises, and the amount of unedible material is to be con- 
sidered. The uneducated provider buys oysters under the 
impression that he is furnishing food of high value, and does 
not distinguish between potatoes and rice. 

In the present state of our knowledge, the best use to which 
we can put such tables and analyses is as a check against gross 
errors of diet, which are found with alarming frequency espe- 
cially among children and students, those who can least afford to 
make them. References will be found in the Bibliography to 
works for further study along these lines. 

Dietaries. — A dietary is simply a known amount of food of 
known composition per person per day, week, or month. 

What is called a standard dietary is such a combination of 
food-materials as shall furnish the amounts held to be neces- 
sary. The following are examples of such standard dietaries: 



FOOD IN RELATION TO HUMAN LIFE 



121 



Approximate amounts 
required daily by 


Nitrogenous, 
grams. 


Fats, 
grams. 


Carbohydrates, 
grams. 


Calories. 


Child of 6-9 


62 

78 

IOO 

100 

125 


45 
45 
75 
90 

125 


200 

281 
380 

450 

500 


1593 
1890 
2665 
3092 
3725 


Child of 9—14 


Adult at rest 


Adult at moderate work . . 
Adult at hard work 



(In feeding experiments from 10 to 20 per cent more must be allowed for waste 
and indigestibility.) 

From the table on page 118 may be selected such food as will 
give the required quantities in variety enough to suit any taste. 
That which the table cannot give is the per cent of each which, 
under any given condition, will be utilized by the person fed. 
The strength of the digestive juices, exercise, fresh air, the 
cooking, the mixing of the foods, the habits of mind as to food, 
the customs of the family, all influence this utilization, so that 
other means must be restored to in order to gain an idea of 
what is practicable. This is done by taking account of the food 
of persons free to choose; of those in different countries, in 
different circumstances, and using a great variety of materials. 
Since Voit made his standard dietary in 1870, many hundreds, 
at least, have been so gathered in the United States alone — 
more than two hundred since 1886. All the information thus 
gained goes to confirm the theoretical standard, and also to 
show how much depends upon suitable preparation and com- 
bination. These last two things help each other. 

As food is ordinarily prepared, about 10 per cent must be 
deducted for indigestibility in a customary mixed diet, and 
about 10 per cent more for the refuse or waste of food as pur- 
chased, so that of the total pounds of meat, vegetables, and 
groceries some 20 per cent is of no final service in the body. It 
is immaterial whether this amount is subtracted from the final 
calculation or whether the higher figures be taken, that is, 
whether 125 grams of proteid as purchased or 100 grams final 
utility is used. There will be an unknown limit in either case. 
According to late experiments 100 grams of proteid is high. 



122 AIR, WATER, AND FOOD 

The waste of fats is less in proportion as the dietary is a restricted 
one. 

Knowledge of Food Values Necessary. — The most serious 
aspect of the food question is that the taking of it is voluntary, 
not, like air, a necessity beyond control, and that the most 
fantastic ideas are allowed to rule. The day-laborer is in little 
danger, since his food demand is made strong by out-of-door 
exercise; but the student who shuts himself up in hot, close 
rooms, and who does not look upon food as his capital, but only 
as a disagreeable task or an amusement, is in great danger, as 
is he who, having heard that one can live on a few cents a day, 
proceeds to try it without knowledge, and suffers a loss of effi- 
ciency for years or for all his life. 

It is not nearly so difficult to acquire a working knowledge 
of food values as of whist or golf, so that on entering a restaurant 
a suitable menu may be made up within one's allowance. It 
is only necessary to correct prevailing impressions and rein- 
force one's experience. 

Figs, dates, raisins and prunes are apt to be regarded as 
luxuries instead of as rich food-substances of a most digestible 
kind when freed from skin and seed. Nuts are a much neg- 
lected form of wholesome food, admirably suited to a winter 
table from their richness in fat, and also furnishing muscular 
energy, as is seen in the agile squirrel, and is proved by many 
human examples. With nuts, however, must be taken fruits 
or other bulky foods, to balance the concentration. The some- 
what compact and oily substance must be finely divided and 
freed from its astringent skin. 

In distinction from these rich foodstuffs, we find oranges, 
apples, etc.; the usual garden vegetables, asparagus, lettuce, 
etc., which while they fill an important place in the dietary, 
add little directly to the energy of the body and need not be 
considered except as, by their flavor or aesthetic stimulus, they 
add to the efficiency of the rest. 

The foods which furnish the greatest nutrition for the least 
money are such materials as corn meal, wheat flour, milk, 



FOOD IN RELATION TO HUMAN LIFE 1 23 

beans, cheese and sugar. The expensive cuts of meat, high- 
priced breakfast cereals and the like, add but little to the nu- 
tritive value but greatly increase the cost of living. A meal of 
lettuce dressed with oil, eaten with bread and cheese, fulfils all the 
requirements of nutrition, and may cost five cents. The same 
food value from sweet breads, grape-fruit, etc., might cost a 
dollar. Incorrect ideas in regard to food values, and prejudice 
inherited or acquired against certain foods, have too often 
resulted in excluding wholesome and nutritious articles from 
the dietary and decreasing thereby the efficiency of the human 
machine. 



CHAPTER VIII 

THE PROBLEM OF SATE FOOD. ADULTERATION AND 
SOPHISTICATION 

Adulteration grows largely, if not almost entirely, from ex- 
cessive competition. Nearly every article of common food has 
been found at one time or another to be adulterated, yet manu- 
facturers testify that they willingly would stop this addition of 
foreign material if they could be sure that their competitors 
would stop also. Other causes there are also: demands for 
goods out of season; for perishable products which must come 
many miles; the failure of the supply of a given substance to 
meet a continuing demand; all of these lead to adulteration, 
imitation and substitution. 

To many people otherwise intelligent, the term adulterated food 
is synonymous with poisoned food. With others, thanks to 
alarming newspaper articles, not wholly disinterested, the general 
impression is far beyond the reality. It is not necessary to 
use poisonous or even deleterious material; it needs only to mix 
with the food material some substance cheaper but harmless, 
to make some change in the outward appearance of the article 
so that people shall not recognize the familiar substance, and 
then to herald far and wide the discovery of a new process by 
which the food value is greatly enhanced. "Things are not 
what they seem" is nowhere more true than in the case of 
foods. 

Definition of Adulteration. — To adulterate is "to debase," "to 
make impure by an admixture of baser materials." The word 
"adulterated " refers to any food to which any foreign substance, 
not a proper portion of the food, has been added. It does not 
matter whether the added material is of greater value than the 
food itself. The addition of coffee to cereal or substitute coffees, 

124 



ADULTERATION AND SOPHISTICATION 125 

is properly held to be an adulteration. Deterioration should not 
be mistaken for adulteration. People who are not wholly familiar 
with the appearance of a food or the chemical and physical 
changes which it may undergo, think that if it does not taste just 
right or look just right that it must be adulterated. Appearance 
has slight relation to the purity of the article in these days of 
paint, polish and powder. 

Some forms of adulteration are more properly described under 
the head of misbranding, that is, referring to foods incorrectly de- 
scribed by the label. While the significance is not exactly the 
same as that of the word adulterated, yet the two may sometimes 
be applied to the same product. For instance, the addition of 
starch to sausage to conceal the use of excessive amounts of water 
and of fat constitutes an adulteration, which would not be the case 
if the article were properly branded to show the presence of the 
added "filler." 

To adulterate the coin of the realm or the liquor of the bar with 
a baser metal or an imitation whisky is a heinous offence. So is 
the mixture of milk with the baser article, water, which thereby 
lowers its food value. But the "wretched sophistry" which ob- 
scures the nature of things on a package of prepared food mis- 
leads more persons and inflicts more injury upon the community 
than the other, yet goes unrebuked. The most barefaced asser- 
tions are printed in magazines, and "pure-food shows" only whet 
the appetite for something new. 

Legal Definition of Adulteration and Misbranding. — In the 
Federal Pure Food Law, commonly known as the Food and Drugs 
Act of June 30, 1906, adulteration and misbranding are thus 
defined : 

Sec. 7. That for the purposes of this Act an article shall be 
deemed to be adulterated: 

In the case of food: 

First. If any substance has been mixed and packed with it so , 
as to reduce or lower or injuriously affect its quality or strength. 

Second. If any substance has been substituted wholly or 
in part for the article. 



126 AIR, WATER, AND FOOD 

Third. If any valuable constituent of the article has been 
wholly or in part abstracted. 

Fourth. If it be mixed, colored, powdered, coated, or stained 
in a manner whereby damage or inferiority is concealed. 

Fifth. If it contains any added poisonous or other added dele- 
terious ingredient which may render such articles injurious to 
health : Provided, That when in the preparation of food products 
for shipment they are preserved by any external application ap- 
plied in such manner that the preservative is necessarily removed 
mechanically, or by maceration in water, or otherwise, and direc- 
tions for the removal of said preservative shall be printed on the 
covering or the package, the provisions of this Act shall be con- 
strued as applying only when said products are ready for con- 
sumption. 

Sixth. If it consists in whole or in part of a filthy, decomposed, 
•or putrid animal or vegetable substance, or any portion of an 
animal unfit for food, whether manufactured or not, or if it is the 
product of a diseased animal, or one that has died otherwise than 
by slaughter. 

Sec. 8. That the term "misbranded," as used herein, shall 
apply to all drugs, or articles of food, or articles which enter into 
the composition of food, the package or label of which shall bear 
any statement, design, or device regarding such article, or the 
ingredients or substances contained therein which shall be false or 
misleading in any particular, and to any food or drug product 
which is falsely branded as to the State, Territory, or country in 
which it is manufactured or produced. 

That for the purposes of this Act an article shall also be deemed 
to be misbranded : 

In the case of food : 

First. If it be an imitation of or offered for sale under the dis- 
tinctive name of another article. 

Second. If it be labeled or branded so as to deceive or mislead 
the purchaser, or purport to be a foreign product when not so, 
or if the contents of the package as originally put up shall have 
been removed, in whole or in part, and other contents shall have 



ADULTERATION AND SOPHISTICATION 127 

been placed in such package, or if it fail to bear a statement on 
the label of the quantity or proportion of any morphine, opium, 
cocaine, heroin, alpha or beta eucaine, chloroform, cannabis 
indica, chloral hydrate, or acetanilide, or any derivative or prep- 
aration of any such substances contained therein. 

Third. If in package form, and the contents are stated in terms 
of weight or measure, they are not plainly and correctly stated on 
the outside of the package. 

Fourth. If the package containing it or its label shall bear any 
statement, design, or device regarding the ingredients or the sub- 
stances contained therein, which statement, design, or device shall 
be false or misleading in any particular : Provided, That an article 
of food which does not contain any added poisonous or deleterious 
ingredients shall not be deemed to be adulterated or misbranded 
in the following cases : 

First. In the case of mixtures or compounds which may be 
now or from time to time hereafter known as articles of food, 
under their own distinctive names, and not an imitation of or 
offered for sale under the distinctive name of another article, if 
the name be accompanied on the same label or brand with a state- 
ment of the place where said article has been manufactured or 
produced. 

Second. In the case of articles labeled, branded, or tagged 
so as to plainly indicate that they are compounds, imitations, 
or blends, and the word "compound," " imitation," or " blend," 
as the case may be, is plainly stated on the package in which 
it is offered for sale: Provided, That the term blend as used 
herein shall be construed to mean a mixture of like substances, 
not excluding harmless coloring or flavoring ingredients used 
for the purpose of coloring and flavoring only: And provided 
further, That nothing in this act shall be construed as requir- 
ing or compelling proprietors or manufacturers of proprietary 
foods which contain no unwholesome added ingredient to dis- 
close their trade formulas, except in so far as the provisions of 
this act may require to secure freedom from adulteration or 
misbranding. 



128 AIR, WATER, AND FOOD 

Extent of Adulteration. — In any discussion of the extent to 
which adulterated foods are sold it must be borne in mind that 
the adulterated articles make up only a relatively small propor- 
tion of the food that actually passes over the counter. Flour, for 
example, is seldom adulterated; pepper, mustard and vanilla ex- 
tract often are. For one pound of these substances sold, iooo 
pounds or more of flour go out from the store. Figures given in 
official reports of food inspection do not represent the case exactly, 
because the inspectors are trained men, and purchase samples of 
those lines of goods which experience has shown them to be most 
likely to be adulterated. Brands of foods which they have reason 
to believe are pure they do not sample. Estimated on the total 
quantity sold, it is doubtful if more than 5 to 10 per cent of the 
food sold is adulterated in any way, and these figures would un- 
doubtedly be much too high for those states in which there is a 
well-enforced system of food inspection. 

Character of Adulteration. — Much of the present propaganda 
in the interests of pure food and the movement for the protection 
of the consumer can be summed up in three words: "An Honest 
Label." In many cases an accurate and true statement of the 
contents of the can or package is the only protection needed by 
the consumer, and is fully as efficient as well as much cheaper 
than prosecutions or restrictive measures. Many of the terms 
used on food packages deceive only the ignorant purchaser. 
"Strictly pure" is a well-understood trade term, with a meaning 
known to the initiated; the words "Home-Made" may cover 
some of the most highly developed products of synthetic organic 
chemistry. 

The cases in which the adulteration is of a character dele- 
terious to health are fortunately few. The use of canned goods 
brings certain dangers in the dissolved metals from the cans or 
from the solder, also from a careless habit of allowing foods 
to stand in the opened tins. The liking for bright green pickles 
and peas leads to coloration by copper salts. 

So rapidly do new substances come upon the market that it is 
of little use to put into a general text-book definite statements of 



ADULTERATION AND SOPHISTICATION 129 

the quality of many foods. A baking-powder or a spice which is 
honestly made to-day may next week pass into the hands of un- 
scrupulous dealers who please the public and thereby salve their 
consciences. 

To furnish what the people think they want has been the rule 
from the days of an earlier generation of grocers, who divided a 
barrel of cooking-soda in halves and set one-half on one side of 
the store for "saleratus" and the other on the opposite side for 
soda, so that there should be no suspicion in the mind of the cus- 
tomer that the packages came from the same barrel, and yet each 
might satisfy his individual preference. 

Names that have passed down from a former generation as 
being above reproach are now found to cover adulterated goods. 
The trademark has passed into other and less scrupulous hands, 
and the new owners do not hesitate to trade upon the reputation 
earned by their predecessors. There are, however, several phases 
of the subject that should be briefly mentioned. 

Breakfast Foods. — The craving for something new to stimulate 
a jaded appetite already spoiled by endless variety and bad com- 
binations has led to the manufacture of a cereal preparation for 
nearly every day in the year, regarding some of which the state- 
ment is made that they are "predigested." No better commen- 
tary on the laziness or wilful ignorance of American providers 
could be made than this. Little do the people know about wheat 
or cooking if they suppose that grain can be changed by manipu- 
lation in any kind of machine so as to give greater food value than 
was contained in the grain. While it is true that some of these 
preparations are far better than the half-cooked grains found on 
so many tables, the fact remains that it is the cook and not the 
substance which is poor. The false statements on food packages 
of all kinds are so absurd that they would defeat their own pur- 
pose were they viewed in the light of common sense. It is not 
always best to have food which is too easily digested. 

A predigested food is quickly absorbed into the circulation, 
and hence a small quantity causes a sensation of fulness and satis- 
faction, which, however, soon passes away and a faintness results. 



13© AIR, WATER, AND FOOD 

This is especially true of the sugars and dextrins. Frequent 
meals should go with easily absorbed foods. The rapid digestion 
is the cause of much pernicious eating of sweets between meals, 
which satisfies the appetite for the time being and prevents sub- . 
stantial quantities of other foods being taken at the time they 
are offered. 

From a study of analyses of a large number of foods the fol- 
lowing conclusions are drawn by F. W. Robison: * 

i. The breakfast foods are legitimate and valuable foods. 

2. Predigestion has been carried on in the majority of them 
to a limited degree only. 

3. The price for which they are sold is as a rule excessive and 
not in keeping with their nutritive values. 

4. They contain, as a rule, considerable fibre which, while 
probably rendering them less digestible, at the same time, may 
render them more wholesome to the average person. 

5. The claims made for many of them are not warranted by 
the facts. 

6. The claim that they are far more nutritious than the wheat 
and grains from which they are made is not substantiated. 

7. They are palatable as a rule and pleasing to the eye. 

8. The digestibility of these products as compared with highly 
milled goods, while probably favorable to the latter, does not give 
due credit to the former, because of the healthful influence of the 
fibre and mineral matter in the breakfast foods. 

9. Rolled oats or oatmeal as a source of protein and of fuel is 
ahead of the wheat preparations, excepting of course the special 
gluten foods, which are manifestly in a different class. 

In general, the cost of these foods is low if they are considered 
merely as confections to please the taste, but they are expensive 
foods regarded as substitutes for the ordinary cereal products. 

This is well shown in the following table in which the fuel 
value of breakfast foods and other common food products ob- 
tained for a given sum is graphically compared. 

* Mich. Agr. Expt. Sta., Bull., 211 (1904). 



ADULTERATION AND SOPHISTICATION 



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132 AIR, WATER, AND FOOD 

Colors and Preservatives in Food. — For many years such sub- 
stances as alcohol, vinegar, sugar, salt, and the like, have been 
used to preserve food. Such materials are commonly held to be 
harmless to persons of sound digestion if used in moderate 
amounts. Within recent years, however, there has been a con- 
stantly increasing tendency toward the use in food products of 
such powerful antiseptics as formaldehyde, salicylic and benzoic 
acids and their salts, and boric acid. An important distinction 
to be borne in mind between this class of preservatives and those 
first named is that the former when used in food in quantity suffi- 
cient to preserve it make their presence known to the consumer 
by either their taste or odor. With the chemical preservatives, 
however, an intimation of their presence is conveyed to the con- 
sumer only by a statement on the label. It is the general feeling 
among those engaged, in the enforcement of the food laws that 
the common use of these preservatives should be forbidden, or 
that they should be allowed only under certain definite restric- 
tions. The question is not one of their possible harmful effect 
only, although it cannot be successfully denied that their unre- 
stricted use would lead to grave danger to health, especially in the 
case of invalids and children, or those with various degrees of 
digestive efficiency. It seems reasonable to infer that the proc- 
esses of digestion, being largely the result of bacterial and 
enzymic action, will be retarded or interfered with to a greater 
or less extent by substances which inhibit bacterial action in 
food. 

There is, however, another reason for objecting to the use of 
chemical preservatives. By their use much food that is unwhole- 
some and unfit for consumption can be, and is, placed upon the 
market with no warning to the consumer. "The man who adds 
formaldehyde to his milk takes down the danger signal, but does 
not remove the danger." 

Similarly, objections can be made to the use of coal-tar colors 
in foods. There are hundreds of food packages which would 
never leave the grocers' shelves were it not for the fact that by 
the use of artificial color their true composition and the actual 



ADULTERATION AND SOPHISTICATION 133 

nature of the materials from which they are made is hidden. 
Apart from any question as to the harmfulness of these dyes 
there is ample reason for their use being strictly regulated by 
official action, in that their use except under such supervision 
allows the manufacturer to sell inferior articles under the appear- 
ance of standard foods; it permits the customer to be misled as 
to the strength and purity of the product that he buys; the age 
and past history of the product may be made a sealed book; 
finally, by the use of coloring, an unwholesome and improper 
food may be put upon the market. 

Summary. — The chief dangers in food are from wrong pro- 
portions of proteid, fat, and carbohydrates, from fermentable and 
irritating decompositions, from bad methods of cooking and 
unsuitable combinations, from transmission of micro-organisms 
either by exposure to dust or by contact with filthy hands or ves- 
sels, to a favorable medium for the growth of pathogenic germs, 
from unsuitable food scientifically disguised. 

From this hasty survey it will be seen how little danger to 
health is incurred if only reasonable care is taken and if the always 
doubtful articles are avoided. 

Take, for instance, that most commonly adulterated class, 
spices. Who will say that it may not be better to eat corn and 
buckwheat and ground peas than pure pepper? Rice is certainly 
a more wholesome food than ginger, and starch than soda. Glu- 
cose is even more easily absorbed than cane-sugar. These are 
cases of frauds on the pockets, but possibly blessings in disguise 
for the stomachs. When any community is so ignorant as to per- 
mit of such glaring cases of adulteration as coal-tar dyes in food, 
and gypsum in cream of tartar, they deserve to suffer. It is 
knowledge on the part of each intelligent citizen which will mend 
matters, even if it is only that kind of empirical knowledge that 
one is forced to learn in relation to electricity and steam in order 
to live in a modern house. 

This knowledge is now easily obtained through the city, state 
and governmental laboratories, and their publications are acces- 
sible to all who can read and write. There is therefore no excuse 



134 AIR, WATER, AND FOOD 

for general ignorance and credulity as to trade preparations of 
foods, any more than for the degrading habit of purchasing patent 
medicines to remedy the ills caused by the misuse of food. Both 
together form the saddest commentary on human weakness and 
lack of rational thought. 



CHAPTER IX 

ANALYTICAL METHODS 

In the discussion of the methods employed for the examination 
of food-materials, only a few typical substances have been con- 
sidered, and the processes given are such as to bring into promi- 
nence the scientific aspect rather than the technical detail of the 
subject; at the same time it is hoped that a sufficient variety of 
methods is given to enable the student to gain considerable expe- 
rience in the necessarily short time which can be alloted to the 
subject. 

Both on account of its importance as a food-material and 
on account of its availability for the various tests, milk has been 
chosen as a type of animal food; moreover, it may be made to 
serve as an excellent example of the changes to which food-ma- 
terials are liable through the growth of the micro-organisms. 
The analysis of milk includes determinations of specific gravity, 
water, or total solids, ash, fat, proteids and sugar, the separation 
of casein and albumin, and the detection of preservatives, color- 
ing matters, and added water. 

The breakfast cereals are taken as typical of vegetable foods. 
The examination which may be made of this class includes the 
determination of moisture, ash, fat, nitrogen and proteids, 
starch, cellulose, and the products of peptonization and sacchari- 
fication. 

The nature and composition of the various fats and oils is 
briefly illustrated by the examination of butter and the deter- 
mination of the principal " constants " of the butter-fat. 

The results of fermentation are illustrated by the deter- 
mination of alcohol in beer, wine, meat extracts, patent medi- 
cines ard " temperance drinks," flavoring essences and the like. 
The determination of the relative proportion of volatile and 

135 



136 



AIR, WATER, AND FOOD 



fixed acids, of the saccharine products of malting, and of volatile 
oils or flavoring principles, is also instructive. 

A more elaborate discussion of the methods used in food 
analysis and of the interpretation of results will be found in 
the larger works upon the subject. As reference books for the 
use of the student in the laboratory, the following, in the author's 
experience, have been found especially helpful: Leach: Food 
Inspection and Analysis; Sherman: Organic Analysis; Rolfe: 
The Polariscope in the Laboratory; Bulletin 107, Bureau of 
Chemistry. 

MILK 

Milk is a food material of somewhat complex and variable 
composition but can be described as essentially an aqueous 
solution of milk sugar, mineral salts and soluble albumin con- 
taining suspended globules of fat and partially dissolved casein. 

General Composition. — In approximate figures the average 
percentage composition of milk may be stated : 

Per cent 
Total solids 12.8 



Fat 3 

Protein 3 

Ash o 

Milk sugar 4 

Solids not fat 9 



From these figures there may be in normal milk quite decided 
variations and figures have been reported which differ widely 
from them, some of the discrepancies of the older analyses being 
undoubtedly due to the imperfect methods of analysis employed. 

Lythgoe * states that all milk completely drawn from healthy 
cows will fall between the following limits : 





Extreme limits, 
per cent. 


Usual limits, 
per cent. 


Herd milk, 
per cent. 


Total solids 


IO. O-17.O 
2.2- 9.O 
2.1- 8.5 
0.6- O.9 
4.O- 6.0 
7-5-II.O 


10. 5-16.0 

2.8- 7.0 

2-5- 4-5 
0.7- 0.8 

4-2-5-5 
7.7-10.0 


II. 8-15.O 
3.2- 6.0 
2.5- 4.0 
0.7- 0.8 

4-3- 5-3 
8.0- 9.5 


Fat 


Protein 


Ash 


Milk sugar 


Solids not fat 





* Bull. Mass. State Bd. Health, 1910, p. 419. 



ANALYTICAL METHODS 



137 



Variations in Composition. — Besides variations in compo- 
sition which may be due to individual cows there are also certain 
well-established differences due to environment or to racial influ- 
ences. Among the more important of these are: 

(1) TJie Breed of the Cow. — Some breeds yield quantity, 
others quality. The Jersey and Guernsey cattle, for instance, 
give comparatively small quantities of milk rich in fat; the 
Holstein cows, on the other hand, yield much larger amounts of 
milk of decidedly lower solids and fat content. These differ- 
ences are well summarized in the following table based on data 
collected by the Massachusetts Board of Health.* 



Breed. 


Specific 
gravity. 


Total 

solids, 

per cent. 


Fat, 
per 
cent. 


Protein, 

per 

cent. 


Ash, 

per 

cent. 


Solids 
not fat, 
per cent. 


Milk 

sugar, 

per cent. 


Jersey 

Guernsey 

Ayrshire 

Dutch Belt.. . 
Holstein 


I-034 
I-034 
I.032 
I.032 
I.032 


14-57 

14.40 
12.57 
12.03 
11.96 


5.40 
5.00 
4.00 
3.60 

3-35 


3-54 

3-77 
2.90 
2.62 
2.99 


O.78 
O.77 

0-77 
O.68 
O.69 


9.17 
9.40 
8-57 
8-43 
8.6l 


4.85 
4.86 
4.90 
5.00 
4.89 



If individual differences are eliminated and only fully drawn 
mixed milk from herds is considered, the variation due to breed 
is the factor of the greatest influence in permanently affecting 
the composition of milk. 

(2) The Time of Year. — The poorest milk is produced during 
the spring and early summer months, the richest during the 
seasons of autumn and early winter, when the cattle are getting 
a smaller proportion of green feed. This difference is clearly 
shown in the following table f which gives the seasonal average 
for 16 years: 





Total solids, 
per cent. 


Fat, 
per cent . 


Solids not fat, 
per cent. 


Nov.— Jan 


I3-04 
12.72 
12.66 
13-03 


4. II 
3-88 
3-89 
4-25 


8-93 
8.84 
8-77 
8.78 


Feb. -Apr 


May — Aug 


Oct. -Nov 





* Bar. of Chem., Bull. 132, p. 129. 

f Richmond: Dairy Chemistry, p. 126. 



138 



AIR, WATER, AND FOOD 



This variation in composition of milk between the pasture-fed 
and the stall-fed season has in the past received legal recognition 
in the fixing of milk standards. In Massachusetts for many 
years the legal standard for total solids was set at 13 per cent 
in the winter months and at 12 per cent in the summer season. 

(3) Time of Day. — Milk which has been drawn in the even- 
ing is nearly always richer in fat than the morning milk as shown 
in the following averages: 





Specific 
gravity. 


Total solids. 


Fat. 


Morning milk 


I.0322 
1-0318 


12.53 
12.94 


3-63 
4.04 


Evening milk 



(4) "Fore" milk vs. "strip pings." — If different portions of 
the whole quantity of milk obtained at a single milking are ex- 
amined separately they will be found to show marked differences 
in fat content, especially as between the first and last portions. 
The other constituents of the milk do not vary so greatly as 
the fat. The first portions of milk, the "fore" milk, contain 
much less fat than do the last portions or "strippings." The 
following figures, due to Van Slyke, illustrate this point: 





Per cent of fat in milk. 




Cow 1. 


Cow 2. 


Cow 3. 


First portion drawn 


O.90 
2.60 

5-35 
9.80 


I.60 
3.20 
4.10 
8.IO 


1 .60 


Second portion drawn 


3-25 
5.00 


Third portion drawn 


Fourth portion drawn (strippings) . 


8.30 



This difference in composition is explained by the separation 
of the milk while in the udder of the cow, cream rising to the 
top just as would happen if the milk stood in a vessel, hence 
being drawn last. Dishonest dairymen have in the past taken 
advantage of this fact in adulteration cases, by having the cows 
partially milked in the presence of unsuspecting witnesses, the 
resulting " known purity" milk being thus largely "fore" milk. 



ANALYTICAL METHODS 139 

In general it will be found that to whatever causes the varia- 
tions noted in the composition of milk are due, the differences 
are shown much more in the fat than in any other constituent. 
The protein is also variable, although to a somewhat less extent, 
and the milk sugar and ash are much more nearly constant. 

METHODS OF ANALYSIS 

Preparation of the Sample. — Since the cream will rise on a 
sample of milk sufficiently in five minutes to destroy the uni- 
formity of the sample, great care must be used in taking a portion 
for analysis to ensure that it represents a fair average of the 
milk. The best way is to pour the milk from the containing 
vessel into another and back again several times, or if this is 
impracticable it should be thoroughly stirred before being sam- 
pled. If the analytical sample has stood for any appreciable 
time it should be mixed by pouring back and forth before a 
portion is removed to test, otherwise concordant results cannot 
be obtained. Do not shake the sample since this tends toward 
a separation of the fat. 

Specific Gravity. — This is usually taken with a special form 
of hydrometer, known as a lactometer. The Quevenne lactom- 
eter has a scale graduated into 25 equal parts, extending from 
15 to 40, corresponding to specific gravities from 1.015 to 1.040. 
The best form of instrument is that provided with a thermometer. 

The lactometer is graduated to give correct results at 6o° F. 
(15. 6° C.) and the reading should be made at approximately 
that temperature, between 55 and 65 degrees, and then corrected 
to standard temperature. This may be done by adding 0.1 
to the reading for each degree F. above 6o° F., or subtracting 
0.1 for each degree F. below 6o° F. If the temperature is 
read in Centigrade degrees the correction may be made by the 
table on page 216. 

The New York Board of Health lactometer has a scale reading 
o in water, and 100 in milk with a specific gravity of 1.029, which 
is taken as the lowest limit for pure milk. The instrument is 
used in the same manner as the Quevenne lactometer and the 



140 AIR, WATER, AND FOOD 

readings can readily be converted into degrees of the latter 
instrument. 

Notes. — The specific gravity of milk fat is about 0.93 ; of the 
solids not fat approximately 1.5. The specific gravity of the 
milk itself is thus a function of the two; the former lowers it, 
the latter increases it. As would be expected from the variable 
composition of milk, the specific gravity is also a variable. The 
values for normal milk from a herd, however, will usually fall 
between 1.030 and 1.034. 

Taken by itself the specific gravity is of little value in showing 
adulteration. The addition of water lowers the specific gravity 
of milk; the removal of cream raises it, this being the lighter 
portion of the milk. It is therefore theoretically possible by 
skilful manipulation to both skim and water a sample and still 
have its specific gravity correspond to that of normal milk. 
Such a sample would, however, be readily recognized by one 
familiar with the appearance of the genuine product. 

The lactometer reading is of value in rapid analysis of milk 
for calculating the solids in connection with the Babcock method 
of fat determination (see page 148). 

Total Solids. — Use a platinum dish having a flat bottom 
about 2 \ inches in diameter. Ignite and weigh the dish accu- 
rately, then add about 5.1 grams to the weights on the balance- 
pan. With a pipette deliver 5 c.c. of the well-mixed milk into 
the dish and weigh the whole as rapidly as possible to the nearest 
milligram. Evaporate the milk to dryness on the water-bath 
and then dry it in the oven at ioo° C. to constant weight. Three 
hours drying is usually sufficient. 

Notes. — It is important that the milk should be dried in a 
thin layer, so that the removal of the water shall take place as 
quickly as possible. Under these conditions the residue ob- 
tained is nearly white, but if the process be prolonged, it may 
have a brownish color from the caramelization of the sugar. 

If it is not desired to determine ash on the same weighed 
portion as used for the solids, lead foil dishes or tin blacking 
box covers may be used instead of platinum dishes. 

Ash. — Ignite the platinum dish containing the residue from 



ANALYTICAL METHODS 



141 



the preceding determination at a low red heat until the ash is 
white or of a uniform light gray color. This may be done in a 
muffle furnace at a temperature not exceeding about 6oo° C, 
or over a burner carefully regulated so that the dish is nowhere 
heated above the slightest visible redness. 

The ash, after weighing, may be tested 
for boric acid or carbonates as described 
on page 154. 

Fat. — (a) Adams' Paper Coil Method. 
Roll a strip of fat-free blotting paper * 
about 22 inches long and 2 \ inches wide, 
into a loose coil and fasten it by a bit 
of wire. Hold the coil in one hand and 
slowly run on to the upper end of it ex- 
actly 5 c.c. of milk from a pipette. If 
preferred, about 5 grams of milk may 
be weighed quickly in a small beaker, 
and one end of the coil introduced so as 
to absorb the milk, care being taken to 
absorb it as nearly completely as possible. 
The beaker is then quickly re- weighed. 

Place the coil, after charging with the 
milk, dry end downward, in the water 
oven and dry it for two hours, then 
extract it for at least two hours in a 
Soxhlet extractor as shown in Fig. n. J 
Use about 100 c.c. of either petroleum^ { 
ether or anhydrous ethyl ether and weigh 
the flask to the nearest milligram. At 
the end of this time disconnect the appa- Fig. n. 

ratus when the extractor is nearly full of ether, thus recovering 
a large portion of the solvent, and evaporate the remainder 
{away from a flame), conveniently by the electric heater, using 
suction. Dry the fat to constant weight in the water-oven. In 




* Schleicher and Schiill make suitable strips which can be obtained from dealers 
in chemical supplies, or the strips may be previously prepared in the laboratory 
from thick filter paper and extracted with ether before using. 



142 AIR, WATER, AND FOOD 

drying the extracted fat it may be heated for two hours the 
first time, then in one hour periods until the loss of weight is 
not over a milligram. 

Notes. — The only part of the method due to Adams is the 
drying of the milk on porous paper. This is, however, of great 
importance since the absorbent paper exercises a selective 
action on the constituents of milk so that the fat is left on the 
surface of the paper, mixed with only about one-third of the 
non-fatty solids, and hence is more easily extracted; further, 
owing to the greatly increased surface exposed, the extraction 
of the fat is practically complete in a comparatively short time. 

Ethyl ether is the solvent commonly employed but care should 
be taken that it is anhydrous, otherwise small amounts of milk 
sugar will be extracted. For this reason petroleum ether is 
to be preferred as a solvent, although its action is considerably 
slower than that of the other. 

The Adams method is probably the most accurate for fat de- 
termination in milk, but in actual practice is not used so much 
as the more rapid centrifugal methods. 

(b) Babcock Method. — Measure 17.6 c.c. of the milk from a 
pipette into the graduated test bottle; add 17.5 c.c. of sulphuric 
acid (sp. gr. = 1.825) pouring it in slowly so as to form a layer 
beneath the milk. After the acid has thus been added to all the 
bottles mix the milk and acid thoroughly by a rotary motion, 
avoiding the spurting of the liquid into the neck of the bottle. 
Place the bottles in opposite pockets of the centrifuge in even 
numbers and whirl them for five minutes at the proper speed. 
The correct speed varies from 1000 revolutions per minute for 
a 10-inch wheel to 700 for one of 24 inches diameter. Then re- 
move the bottles and add hot water up to the necks, after which 
whirl them again for one minute. Again add hot water until 
the fat rises nearly to the top of the graduations. Whirl again 
for one minute. Then measure the length of the column of fat 
by a pair of dividers, the points being placed at the extreme 
limits of the column, the fat being kept warm, if necessary, by 
standing the bottles in water at 6o° C. If now one point of the 



ANALYTICAL METHODS 143 

dividers is placed at the o mark of the scale on the bottle used, 
the other will indicate the per cent of fat in the milk. 

Notes. — Methods based on centrifugal separation of the fat, 
of which the Babcock method is the pioneer, are by far the most 
rapid and convenient for general use. They have practically re- 
placed the more tedious extraction methods and are universally 
employed in creameries and milk depots. 

When the acid and milk are mixed the mixture becomes hot 
and turns dark colored on account of the charring of the milk 
sugar. The casein is first precipitated and then dissolved. 
The retarding effect of the milk serum solids being thus elimi- 
nated, the fat globules are free to collect in a mass. 

The fat obtained should be of a clear, golden yellow color, and 
distinctly separated from the acid solution beneath it. If the 
fat is light-colored or whitish, often with a layer of white par- 
ticles beneath it, it generally indicates that the acid is too weak 
or that the milk was too cold when the acid was added. A 
dark-colored fat with a sub-stratum of black particles indicates 
that the acid is too strong. The best results will be obtained 
by the use of acid of the strength noted above. 

The capacity of the graduated neck of the bottle between the 
o and 10 marks is 2 c.c. The specific gravity of warm milk fat 
is 0.9, hence 2 c.c. will weigh 1.8 grams or one-tenth of the 
weight of 17.6 c.c. of milk (approximately 18 grams). The 
measurement of the extreme limits of the column of fat, rather 
than to the upper meniscus, is to correct for the small amount of 
fat, 0.1 to 0.2 per cent, that remains in the acid solution. 

Milk which has been preserved with formaldehyde usually re- 
quires a longer time and more vigorous shaking to dissolve the 
curd, on account of the hardening action of this preservative on 
the coagulated casein. It is often advantageous to stand the 
bottles in water at 6o° C. for a time before whirling. Samples 
containing formaldehyde will usually give a violet color when 
the acid is added to the milk. 

(c) Gottlieb Method.* — With a pipette place 5 c.c. of milk 
in a 50-c.c. glass stoppered cylinder and add the following re- 

* Rose: Z. angew. Chem., 1888, 100; Gottlieb: Landw. Vers. Stat., i8q2, 6. 



144 



AIR, WATER, AND FOOD 



agents, being careful to add them in the order given and to 
shake the stoppered cylinder thoroughly after the addition of 
each reagent: i c.c. of ammonia (sp. gr. = 0.96), 5 c.c. of alcohol, 
12.5 c.c. of ethyl ether, and 12.5 c.c. of petroleum ether. Let 
the cylinder stand until the lower layer is free from bubbles — 
several hours if necessary. Transfer the upper layer to a tared 
flask by means of an arrangement similar to a wash-bottle, 
as shown in Figure 12. Adjust the sliding tube until the end 
rests just above the junction of the two lay- 
ers, then by gently blowing force out the 
upper layer into the flask. Repeat the ex- 
traction, using 10 c.c. each of ethyl ether and 
petroleum ether and blowing it off into the 
flask as before. Distill off the solvent and 
dry the residual fat to constant weight in 
the water oven. Dissolve the weighed fat 
in a little petroleum ether. If a residue 
is found, due to a trace of the aqueous layer 
which was blown off with the ether, wash it 
several times in the flask by careful decanta- 
tion with petroleum ether. Finally dry and 
weigh the flask and residue and deduct from 
the previous weight. The difference is the 
weight of purified fat. 
Notes. — All of the successful methods for determining the fat 
by direct extraction from the milk itself involve the complete or 
partial solution of the casein. In the Gottlieb method the 
casein, precipitated from the milk in very finely divided form by 
the alcohol, is dissolved by the ammonia. The fat is dissolved 
by the ethyl ether and the addition of petroleum ether is to 
render less soluble the milk sugar or other non-fatty solids 
which would be dissolved by ethyl ether alone. 

The method, while applicable to whole milk, is especially 
valuable in determining fat in such products as skim milk or 
buttermilk which are low in fat. In such cases it is better to 
use 10 c.c. of milk and double the quantity of reagents. 




ANALYTICAL METHODS 145 

Milk Sugar. — The sugar in milk is most readily determined 
by its reducing action on Fehling's solution. 

Munson and Walker Method.* — Directions. — Measure 25 
c.c. of milk into a 500-c.c. graduated flask. Add about 400 c.c. 
of water, 10 c.c. of copper sulphate solution,! then 35 c.c. of 
tenth-normal sodium hydroxide (or an equivalent quantity of a 
stronger solution) and make up to 500 c.c. Mix thoroughly 
and filter through a dry filter. 

In a Xo. 3 beaker mix 25 c.c. of the Fehling's copper sulphate 
solution and 25 c.c. of the alkaline tartrate solution. Add 50 
c.c. of the milk sugar solution, prepared as above, cover the 
beaker with a watch glass, and heat it upon wire gauze. Reg- 
ulate the flame so that boiling shall begin in four minutes, and 
continue the boiling for exactly two minutes. 

Filter the cuprous oxide without delay through asbestos in 
a weighed Gooch crucible, wash it with hot water until free 
from alkali, pour out the hot filtrate, then wash with 10 c.c. 
of alcohol and, finally, with 10 c.c. of ether. Dry the crucible 
for 30 minutes at the temperature of boiling water and weigh. 
Find the milligrams of lactose monohydrate corresponding to 
the weight of cuprous oxide from Table XII on page 221 and 
calculate the percentage present in the milk. 

Notes. — Before the lactose can be determined by Fehling's 
solution the protein and fat must first be removed. This is 
done by the precipitation with copper hydroxide, the fat being 
carried down mechanically by the precipitated protein. The 
addition of alkali should be such that a slight excess of copper 
still remains in solution, since an excess of alkali will prevent 
the precipitation of part of the protein. The quantity stated 
in the procedure is correct for most milks. 

On account of the considerable dilution of the sample, the vol- 
ume of the precipitated protein and fat need not be considered. 

The general principle upon which all these methods depend 

* /. Am. Chem. Soc, 1906, 663; 1907, 541. 

f 69.28 grams per liter. The copper sulphate solution used in the Fehling de- 
termination may be conveniently employed. 



146 AIR, WATER, AND FOOD 

is based on the fact that certain sugars, among which is lactose, 
have the power of reducing an alkaline solution of copper to a 
lower state of oxidation in which copper is separated as cuprous 
oxide. The copper salt which is found to give the most delicate 
and reliable reaction is the tartrate. The two solutions which 
make up the Fehling's solution are best preserved separately, 
and mixed only when wanted for use, as otherwise the reducing 
power of the solution is liable to change. 

The amount of reduction of the copper salt to the cuprous 
oxide is affected by the rate at which the sugar solution is added, 
the time and degree of heating, and the strength of the sugar so- 
lution; hence the necessity for adopting a definite procedure 
and for taking the results from a table determined by exactly 
the same procedure for varying amounts of the sugar. 

The asbestos which is used should be previously boiled in 
nitric acid and then in dilute sodium hydroxide and thoroughly 
washed. A layer about a centimeter thick should be used in 
the crucible, and a "blank" determination made with the 
Fehling's solution should not show a change in weight greater 
than one-half milligram. After the precipitated cuprous oxide 
has been weighed it may be dissolved in hot dilute nitric acid, 
and the asbestos in the crucible washed and dried as described, 
when it is again ready for use. Do not remove the asbestos 
from the crucible. 

Proteins. Determination of Total Protein. — This is best done 
by the Kjeldahl method. Weigh 5 grams of milk into a Kjeldahl 
flask, add 10 c.c. of concentrated sulphuric acid and three drops 
of mercury and carry out the determination as described on 
page 182. 

The tendency of the alkaline solution to froth during the 
distillation, which is especially noticeable with milk, can be 
prevented by the addition of a piece of paraffin the size of a pea. 
Multiply the per cent of nitrogen by the factor 6.38 to obtain 
the per cent of protein. 

Separation of Casein and Albumin. — The usual method of 
precipitating the casein by acid at a temperature below the 



ANALYTICAL METHODS p 147 

coagulating point of the albumin, while capable of good results, 
is tedious and rather unsatisfactory except after considerable 
experience. The following volumetric method, devised by 
Van Slyke and Bosworth * gives results of almost equal 
accuracy, but requires much less time and skill. 

Measure 20 c.c. of the well-mixed milk into a 200-c.c. grad- 
uated flask and add about 80 c.c. of water. Add 1 c.c. of phenol- 
phthalein solution and tenth-normal sodium hydroxide until a 
faint pink color remains throughout the mixture even after con- 
siderable shaking. Avoid an excess of alkali. 

To the neutralized diluted sample, which should be at a tem- 
perature of 1 8° C. to 24 C, add tenth-normal acetic acid in 
5-c.c. portions, shaking vigorously for a few seconds after each 
addition. After thus adding 25 c.c. and shaking, the mixture 
is allowed to come to rest. If enough acid has been added, the 
casein separates promptly in large, white flakes, and on standing 
a short time, the supernatant liquid appears clear, not at all 
milky. If the addition of 25 c.c. of acid is insufficient to sepa- 
rate the casein properly, add 1 c.c. more of acid and shake; 
continue this addition of acid 1 c.c. at a time, until the casein 
separates promptly and completely upon standing a short time. 
Note the number of c.c. of acid used. 

After the casein is completely precipitated make up the mix- 
tures to the 200-c.c. mark with water, shake thoroughly and 
filter through a dry filter. Filtration should be rapid and the 
the filtrate quite clear. If a marked turbidity is apparent in 
the filtrate, a new sample should be taken and the process re- 
peated, using more acid than before. Titrate 100 c.c. of the 
filtrate with tenth-normal sodium hydroxide and phenolphtha- 
lein to a pink color which remains throughout the solution for 
thirty seconds. Subtracting the number of c.c. of sodium hy- 
droxide from one-half the c.c. of tenth-normal acetic acid added 
will give the c.c. of acid required to precipitate the casein for 

10 c.c. of milk. (1 c.c. of — acetic acid = o. 113 15 gms. of 

casein.) 

* /. Ind. Eng. Chem., 1909, 768. 



148 AIR, WATER, AND FOOD 

Calculation of Milk Solids. — It has long been recognized that 
in normal milk the constituents are present in a fairly constant 
ratio. This being true, it should be possible, having deter- 
mined two factors, to find a third by calculation, or at least 
to show by such calculation a sufficient variation from the 
normal to indicate the adulteration of the sample. For ex- 
ample, given the lactometer reading and fat, to calculate the 
total solids: 

L = the lactometer reading, 

s = increase in lactometer reading by 1 per cent solids not fat, 
/ = decrease in lactometer reading by 1 per cent fat, 
T = total solids, 
S = per cent of solids not fat, 
F = per cent of fat. 

Then L = Ss - Ff, 

Since S = T - F 

L = (T-F)s-Ff, 

whence T = •*■ + F. 

s 

The uncertainty of the calculation lies in the values for 5 and/, 
which, on account of the difference in solution densities of the 
components of the solids not fat, are not absolute constants. 

Based on the principle just stated, various formulas have 
been proposed for the calculation of milk solids. One of the 
simplest of these is that of Hehner and Richmond * 

T = - + 1.2 F + 0.14, 
4 

where T is the per cent of total solids, L the reading of the lac- 
tometer, and F the fat. 

When a number of calculations are to be made, Richmond's 
"Milk Scale" will be found convenient. This is an instrument 
based on the principle of the slide-rule, having three scales, 
two of which, for the fat and the total solids, are marked on 

* Analyst, 1888, 26; 1892, 170. 



ANALYTICAL METHODS 



149 



the body of the rule, while that for the lactometer readings 
is marked on the sliding part. 

A similar relation has been worked out for the protein, so 
that if a constant value be assumed for the ash, the composition 
of a sample may be determined with a fair degree of approxima- 
tion from the two simple determinations of specific gravity and 
Babcock test. 

The relation between the protein and fat has been expressed 
by Van Slyke* as P = 04 (F - 3) + 2.8. Similarly Olsen f 
has proposed the following formula for calculating the protein 
from the total solids (T.S.) : 

T.S. 



T.S. - 



i-34 



These values will naturally be most nearly correct in the case 
of normal average milk. With watered or skimmed milk they 
will be only approximate. 

In the table below the values calculated for a sample are com- 
pared with those actually determined: 



Determination. 



Actual 


values. 


33 




3 


80 


12 


73 





7i 


3 


33 


5 


04 


8 


93 



Calculated values. 



Lactometer reading 

Fat (Babcock) 

Total solids 

Ash 

Proteins 

Milk sugar 

Solids not fat 



12.95, 

0.7 (assumed) 
j 3.12 (Van Slyke) 
I 3 . 29 (Olsen) 

5.16 

9-i5 



Examination of Milk Serum. — The most variable constitu- 
ents of normal milk are the fat and protein, especially the former; 
the least variable are the ash and milk sugar. The milk serum, 
or milk from which the fat and protein have been removed, is, 
therefore, of more uniform composition than the milk itself, 
hence better suited for the detection of adulteration and espe- 

* /. Am. Chem. Soc, igoS, 1182. 
t /. Ind. Eng. Chem., igog, 253. 



150 AIR, WATER, AND FOOD 

daily of added water. The serum may be prepared by adding 
to the milk some suitable precipitant of the protein, as calcium 
chloride, acetic acid or copper sulphate. The clear liquid after 
nitration may be examined for its content of dissolved solids, 
its specific gravity or most conveniently by the immersion 
refractometer. 

The Copper Sulphate Method* — Dissolve 72.5 grams of 
crystallized copper sulphate in water and dilute to a liter. This 
solution should be adjusted, if necessary, so that it will refract at 
36 degrees on the scale of the immersion refractometer at 20 C. 
or have a specific gravity of 1.0443 at 2 °° C. compared with 
water at 4 C. To one volume of the copper solution add 
four volumes of milk, shake well and filter. The filtrate will 
usually be clear after the first few drops have passed through. 
On the clear filtrate either the refraction at 20 C, the specific 

gravity ( — ^ J or the total solids may be determined. 

Notes. — Examination of the copper serum from 150 samples of 
known purity milk gave refractions varying from 36.1 to 39.5, 
while the total solids of the same samples showed a range from 
17.17 per cent to 10.40 per cent and the fat varied from 7.7 per 
cent to 2.45 per cent. 

The minimum values for the copper serum of normal milk 
are 36 degrees for the refraction at 20 C, 1.0245 for the specific 

gravity (— - 1 and 5.28 per cent for total solids. 

If the milk is already soured, it may be filtered and similar 
determinations made on the natural sour serum, which for un- 
watered milk should not refract below 38.3 or have a specific 

gravity at — 5- 1 below 1.0229. 
4 

SPECIAL TESTS FOR ADULTERANTS 

Cane Sugar. — Cane sugar may be present in milk from 
diluted condensed milk used to eke out the supply or may be 
present from calcium saccharate, added as a thickening agent. 
* Lythgoe: Ann. Rpt. Mass. Bd. Health, 1908, 594. 



ANALYTICAL METHODS 151 

It is evident that any considerable amount which had been 
added could be detected by the taste. 

To detect the presence of cane sugar boil about 10 c.c. of the 
milk with 0.1 gram of resorcin and 1 c.c. of strong hydrochloric 
acid for five minutes. The liquid will be colored rose-red if 
cane sugar is present. The color produced by heating should 
not be confused with the pink color which may appear in the 
cold if the milk contain certain coal-tar colors. 

A similar test is the reduction of ammonium molybdate. As 
recommended by Cotton * 10 c.c. of the milk are mixed with 
0.5 gram of powdered ammonium molybdate and 10 c.c. of dilute 
(1 to 10) hydrochloric acid are added. In another tube 10 c.c. 
of milk known to be free from sucrose are similarly treated and 
the tubes placed in a water-bath, the temperature of which is 
gradually raised to about 8o° C. If sucrose is present, the 
milk will gradually turn deep blue, while genuine milk remains 
unchanged unless the temperature approaches the boiling point. 
Cotton states that the reaction will detect as little as 1 gram 
of cane sugar in a liter of milk. 

Note. — Both of these tests, although used to detect cane 
sugar, are in reality tests for levulose, formed in this case by 
the partial inversion of the sucrose. 

Preservatives. — The preservatives most commonly employed 
in milk are formaldehyde, boric acid or borax, and mixtures of 
the two, and possibly hydrogen peroxide and fluorides. Sali- 
cylic acid and sodium benzoate, although largely used in some 
other classes of food materials, have been reported very rarely 
as present in milk. 

Formaldehyde. — This is the ideal preservative for milk, 
being readily used and by far the most efficient. Quantities 
which give a proportion in the milk of from 1 in 10,000 parts 
to 1 in 50,000 are ordinarily employed. Such an amount will 
suffice to preserve the milk for from 24 hours to several days. 
Larger quantities, such as 1 part in 3000, will preserve the milk 
for months. These large amounts, however, would be more or 

* /. Pharm. Chim., 1897, 362. 



152 AIR, WATER, AND FOOD 

less apparent by the taste or odor. A tabular statement show- 
ing the efficiency of formaldehyde in preserving milk as com- 
pared with boric acid, borax and sodium carbonate will be found 
in Leach's Food Analysis. 

Several of the best tests for detecting formaldehyde are de- 
scribed below. These may be applied directly to 10 c.c. of the 
milk, or as suggested in the gallic acid test, a larger quantity, 
25 to 100 c.c, may be distilled and the test applied to the first 
portion of the distillate. 

(1) When the sulphuric acid is added to the milk in making 
the Babcock test for fat, a bluish-violet ring will be noticed 
at the junction of the two liquids when formaldehyde is present. 
One part of formaldehyde in 200,000 parts of milk can be de- 
tected by this test, but it fails when the formaldehyde amounts 
to 0.5 per cent. The test is more delicate if the sulphuric acid 
contains a trace of ferric chloride. 

(2) To 10 c.c. of milk in a small porcelain dish add an equal 
volume of hydrochloric acid (1.20 sp. gr.). Add one drop of 
ferric chloride solution and heat the dish with a small flame, 
stirring vigorously, until the contents are nearly boiling. 
Remove the flame and continue the stirring for two or three min- 
utes, then add about 50 c.c. of water. The presence of formal- 
dehyde will be shown by a violet color which appears in the 
particles of the precipitated casein, the depth of color depending 
on the amount of formaldehyde present. The color should 
be observed carefully at the moment of dilution. This test 
readily shows the presence of one part of formaldehyde in 
250,000 parts of milk, if fresh. 

(3) Gallic Acid Test* — This test has been found by Shermanf 
to be much more delicate than either of the preceding tests. 
25 to 50 c.c. of the milk should be acidulated with phosphoric 
acid and distilled. To the first 5 c.c. of the distillate add 0.2 
to 0.3 c.c. of a saturated solution of gallic acid in pure ethyl 

* Barbier and Jandrier: Ann. Chim. anal., 1, 325; Mulliken and Scudder: Am. 
Chem. J., igoo, 444. 

f /. Am. Chem. Soc, 1905, 1499. 



ANALYTICAL METHODS 153 

alcohol and pour it cautiously down the side of an inclined test 
tube containing 3-5 c.c. of pure concentrated sulphuric acid. 
If formaldehyde is present a green zone is formed at the junction 
of the two layers, gradually changing to a pure blue ring. 

The delicacy of the test is about one part of formaldehyde in 
500,000 parts of milk. 

Notes. — It should be borne in mind that when small amounts 
of formaldehyde are added to milk the ordinary tests will show 
the presence of the preservative for only a short time. For 
example, it has been shown by Williams and Sherman * that 
when formaldehyde was added to milk in the proportion of 1 part 
to 100,000 only a faint test was given after 48 hours standing; 
and that the preservative had entirely disappeared in from three 
to five days. This is due to the gradual formation of conden- 
sation products of the formaldehyde with the proteins of the milk 
which do not respond to the usual reaction. In such a case, it is 
better to distill the milk as directed and apply the test with 
gallic acid to the distillate. The test is thus made more delicate, 
so that the preservative may still be shown when the simpler 
tests have failed. 

Another possible contingency is that some substance may be 
added with the formaldehyde which will interfere with the tests 
for its detection. Both hydrogen peroxide and nitrites prevent 
the reaction of formaldehyde in the usual tests and preserva- 
tives are on the market which are mixtures of formaldehyde 
with hydrogen peroxide or a nitrite. The sulphuric acid test 
and the hydrochloric acid-ferric chloride test can be used to 
show the formaldehyde in the presence of considerably larger 
quantities of nitrites by first removing the latter. Add to 10 c.c. 
of the milk 1 c.c. of a 10 per cent solution of urea, then 2 c.c. 
of dilute (1 140) sulphuric acid and immerse the test tube in boil- 
ing water for two minutes. Cool and carry out the test as usual. 
The reaction between the urea and the nitrous acid may be 
expressed : 

CO (NH 2 ) 2 + 2 HNO2 = C0 2 + 2 N 2 + 3 H 2 0. 

* /. Am. Chem. Soc, 1905, 1497. 



154 AIR, WATER, AND FOOD 

Boric Acid or Borax. — Make 25 c.c. of the milk distinctly 
alkaline with lime water and evaporate to dryness on the water- 
bath. Char the residue over a flame but do not necessarily 
heat it until white. Digest the residue with 15-20 c.c. of water 
and add hydrochloric acid (1.12) until the mixture is faintly 
acid to litmus paper. Filter, and add 1 c.c. of acid in excess. 
Place a strip of turmeric paper in the solution and evaporate to 
dryness on the water-bath. If boric acid or borates are present, 
the paper takes on a peculiar red color, which is changed by 
ammonia to a dark blue-green, but is restored by acid. Excess 
of hydrochloric acid should be avoided, as it turns the paper a 
dirty green when evaporated. This test can also be applied 
to the hydrochloric acid solution of the ash. 

Sodium Carbonate. — Detected in the milk-ash, as on page 
141. If effervescence occurs, test the original milk with rosolic 
acid as follows: Mix 10 c.c. of milk with an equal volume of 
alcohol, and add a few drops of a one per cent solution of rosolic 
acid. The presence of sodium carbonate is indicated by a more 
or less distinct pink coloration. A comparative test should be 
made at the same time with milk known to be pure. 

Salicylic and benzoic acids. — If it is desired to test for these, 
the following method may be employed. To 25 c.c. of milk add 
100 c.c. of water and precipitate the proteins and fat with copper 
sulphate and sodium hydroxide, as described on page 145. 
Filter and add to the filtrate 5 c.c. of concentrated hydro- 
chloric acid. Extract with ether and proceed as outlined on 
page 196. 

Coloring Matter. — The object in adding coloring matter to 
milk is in general to disguise the bluish appearance of skimmed 
or watered milk. For this reason it is rather unusual to find 
added color in the case of milk which is of standard quality, 
although such cases have been reported. 

Formerly the chief color used was annatto, a reddish-yellow 
coloring matter obtained from the seeds of Bixa Orellana, a 
shrub growing in South America and the West Indies. A solution 
of the color in very dilute alkali is employed. More recently 



ANALYTICAL METHODS 155 

various coal-tar dyes and even caramel have been used. The 
latter is, perhaps, not so likely to be found, because its color 
is too brown and not enough yellow to give the desired creamy 
appearance to the milk which is so easily obtained with annatto. 
The coal-tar colors, especially mixtures of yellow and orange 
azo dyes, give very good results. 

Leach * has suggested a general scheme for the identification 
of these colors in milk, which with some modifications which 
experience in the writer's laboratory has shown to be helpful 
in detecting annatto especially, is given below. 

Procedure. — Place about 100 c.c. of the milk in a small 
beaker, add 3-4 c.c. of 25 per cent acetic acid (sp. gr. = 1.04), 
stir thoroughly and allow the beaker to stand quietly on the 
water-bath for about ten minutes, the casein being thus sepa- 
rated as a compact cake. Decant off the whey, squeezing the 
curd as dry as possible with a spatula. Transfer the curd to 
a flask, cover it with ether, stopper tightly, and shake the flask 
violently in order to break up the curd as much as possible. 
Let it stand for several hours, preferably over night. 

Pour off the ether, which contains the annatto, and evap- 
orate {away from a flame) until no odor of ether remains. Add 
5 c.c. of water and then dilute sodium hydroxide until the mix- 
ture, after thorough stirring with a glass rod, is faintly alkaline 
to litmus paper, and filter through a wet filter. If annatto is 
present it will permeate the filter and give it an orange-brown 
color which may readily be seen if the filter is removed from the 
funnel and the fat washed off under the tap. Its presence may 
be confirmed by touching the colored portion of the paper with 
a drop of stannous chloride, which gives a pink color with annatto. 

After pouring off the ether examine the milk-curd for caramel 
or coal-tar color. If the curd is left white, neither of these 
colors is present. If caramel has been used, the curd will be of 
a pinkish-brown color; if the color is due to the coal-tar dye, 
the curd will have a yellow or orange tint. If now some con- 
centrated hydrochloric acid is poured over the curd, the color 

* /. Am. Chem. Soc, igoo, 207. 



156 AIR, WATER, AND FOOD 

will change immediately to a bright pink with the coal-tar colors 
ordinarily used. 

Notes. — When the milk is curdled by the acid, any added color 
is carried down by the curd. When this is subsequently treated 
with ether the fat and annatto are dissolved, leaving any cara- 
mel or coal-tar color still in the curd. Since the detection 
of the two latter colors may depend upon recognizing color in 
the curd, this should always be compared with the curd prepared 
in the same manner from a sample of milk known to be free from 
color. 

The ordinary tests for caramel as used to show its presence 
in distilled liquors or vanilla extract are not sufficiently delicate 
to detect the extremely small quantity which suffices to impart 
the desired shade of color to the milk. The color imparted to 
the curd, however, is characteristic and readily recognized. 

It is possible that coal-tar dyes may be used which do not 
give the pink reaction with hydrochloric acid, since this is char- 
acteristic in general only of the azo class of dyes. Even in 
these cases, however, the orange color of the dye is readily per- 
ceptible in the separated curd. 

Milk colored with an azo dye may occasionally fail to show 
its presence if the sample is old or partly decomposed before 
being tested. This has been shown by Blyth * to be due to the 
reduction of the dye by nascent hydrogen produced by the growth 
of certain anaerobic organisms. 

Interpretation of Results. — Apart from the addition of 
foreign ingredients, such as colors and preservatives, which are 
detected by the specific tests described, the most common forms 
of adulteration are the addition of water and the removal of 
cream. By reference to the table on page 136, it will be seen 
that on account of the variation in the composition of unadul- 
terated cow's milk the detection in all cases is not an easy prob- 
lem. The variation in the fat content, especially, makes it 
more difficult to show with certainty the partial removal of 
cream than the addition of water. 

* Analyst, igo2, 146. 



ANALYTICAL METHODS 



157 



This is well shown in the following table in which "A " is 
a normal milk, U B" the same milk in which the fat has been 
reduced to 3.6 per cent by adding water and "C" the same milk 
in which the fat has been reduced to 3.6 per cent by skimming. 





A 


B 


C 


Total solids 


12.78 
4.00 
2.89 
5.00 
0.71 
8.78 


n-34 

3.60 
2.60 
4-5o 
0.64 

7-74 


12.09 
3.60 
2.91 
4.98 
0. 72 


Fat 


Protein 


Sugar 


Ash 


Solids not fat 


8.61 







It is seen that in sample C it is only the fat that has been 
decreased to any degree. In fact there is nothing in the figures 
given for C to indicate in any way that the sample is not genuine 
milk, while in B the solids not fat are so low as to show the adul- 
teration quite plainly. 

Composition of Milk of Known Purity. — The average com- 
position of milk, together with the usual and the extreme limits 
of variation, have already been stated on page 136. The greater 
number of published analyses of genuine cows' milk have been 
limited to determination of solids, fat and specific gravity. A 
more detailed study, including the constants of the copper 
serum, will be found in the following table,* which includes the 
analyses of 33 samples of known purity milk from individual 
cows, and 4 samples of herd milk, arranged in the order of their 
percentage of total solids. 

In collecting the samples milk was taken from the heaviest 
milkers, so as to include a larger proportion of low-grade milk 
for minimum values. None of the milk could be called excep- 
tionally high grade, as samples were not collected from Jersey or 
Guernsey cows. 

Inspection of this table shows, as would be expected, a great 
variation in the percentage of fat in the individual samples, the 
highest being almost 100 per cent higher than the minimum 
values. The solids not fat are seen to present a much less 

* Lythgoe: Bull. Mass. Bd. Health, 1910, 422. 



158 AIR, WATER, AND FOOD 

variation, and as Lythgoe has pointed out, this variation 
is due very largely to the changes in protein content, the milk 
sugar and ash remaining fairly constant. Upon this fact 
depends the special value of an examination of the milk 
serum. 

In some cases all that may be necessary is to show by the 
analysis that the milk does not conform to the legal standard. 
In certain of the states, however, a legal distinction is made 
between milk which is simply below standard and milk which has 
been actually adulterated by skimming or watering. It is there- 
fore of importance to show by the analysis whether water has 
been added to the milk directly and not through the breed or 
feed of the cow. 

Detection of Watered Milk. — Since in general the water that 
has been added is no different from the water already present 
in the milk it is evident that this form of adulteration can be 
detected only by showing chemical or physical changes in the 
milk that could be ascribed only to the addition of water. Meth- 
ods have been proposed, it is true, based on differences in the 
added water, such as an abnormally high amount of nitrates, 
which might have been derived from the polluted barnyard 
well, but these methods are of little importance. 

(a) Solids Not Fat. — Since the variation in proportion of 
solids not fat in normal milk is much less than the range of 
total solids this is of distinct value in showing added water. 
Although as indicated in the table of limiting values on page 136, 
the value for solids not fat may go as low as 7.5 per cent, this 
is rather uncommon, and a fairer minimum would be 7.7 per 
cent. A value below 7.7 per cent would certainly be suspicious 
of added water and if accompanied by correspondingly low values 
for the constants of the serum could be regarded as direct evidence 
of adulteration. 

(b) Milk Sugar. — As suggested by Lythgoe,* the milk sugar 
may be employed to even greater advantage than the solids not 
fat in showing adulteration. Knowing the percentage of solids 

* Loc. cit. 



ANALYTICAL METHODS 



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AIR, WATER, AND FOOD 



and of fat, the protein may be calculated by the formulae given 
on page 149. Then if 0.7 be assumed as the value for the ash, 
the milk sugar may be determined by subtracting from the 
total solids the sum of the other constituents. The expression 
for the milk sugar would then become 

(1) Milk sugar = T.S. - (F + [0.4 (F - 3) + 2.8] + 0.7). 

(2) Milk sugar = T.S. - (F + [~T.S. - — 1 + 0.7). 

L 1.34J 

The portion of the formula enclosed in brackets is the calcu- 
lated protein in each case. In the case of pure milk the formulae 
for calculating the protein will give very similar results, but 
with adulterated milk they will be divergent, the difference 
increasing with the extent of adulteration. In the case of 
watered milk the calculated milk sugar will be too low, ordinarily 
falling below 4.2 per cent, while, as will be shown later, with 
skimmed milk, the milk sugar will be too high, generally above 4.8 
per cent. 

(c) Milk Serum. — If the preliminary calculation indicates a 
possibility of the samples being watered an examination of the 
serum should be made. This may be done preferably by the 
copper sulphate method, which is described and the minimum 
values for pure milk stated on page 150. The following table 
due to Lythgoe shows the effect of systematic watering on the 
composition of the milk and the constants of the serum in the 
case of a milk which was above the average in solids not fat 
and refraction. 

COMPOSITION OF A SAMPLE OF MILK SYSTEMATICALLY 
WATERED 



Added 


Solids 

(per 

cent). 


Fat (per 
cent). 


Solids not 
fat (per 
cent). 


Copper serum. 


water 

(per 

cent). 


Refrac- 
tion, 20°. 


Specific 

gravity, 

20° 

4° 


Solids 

(per 

cent). 


O 
IO 
20 

3° 
40 

50 


13.18 

11.86 

IO-S4 

9-23 

7.91 

6-59 


4.20 
3-78 
3-36 
2.94 
2.52 
2. 10 


8.98 
8.08 
7.18 
6.29 
5-39 
4-49 


38.5 
36.4 
34-4 
32.4 
30.6 
28.6 


I .0272 
I . 0249 
I.0233 
I .02II 
I .0194 
I. 0174 


6.09 
5-57 
5-05 
4-56 
4.10 
3-54 



ANALYTICAL METHODS 161 

It is seen that each 5 per cent of added water lowers the 
refraction by one scale division, hence with average milk, 
refracting below 38 degrees, 10 per cent of added water could 
be detected, and with rich milk 15 per cent can usually be 
found. 

Detection of Skimmed Milk. — Watering milk does not in 
general change the relation of the various constituents to one 
another, since these are all reduced in the same proportion, 
but removing the fat does change these ratios. It is immaterial 
whether the milk is skimmed by the actual removal of some of 
the fat or whether separator skim milk is added to normal milk. 
In either case the resulting product will have its fat content 
largely reduced, while the proteins and sugar suffer but little 
change. In normal milk, especially in the mixed milk of a herd, 
the percentage of fat is rarely less than the protein (see table, 
page 159). In 5500 analyses of American milks compiled by 
Van Slyke, with a fat content between 3 and 5 per cent, the 
average amount of fat was 3.92 per cent and the average amount 
of proteins 3.20 per cent. If such milk be skimmed the fat may 
be reduced to 1 per cent or even to 0.1 per cent but the protein 
content will still be approximately the same as before. In the 
calculation of milk sugar by the formulae given on page 160, 
the same effect will be noticed, that is, the skimming will 
lower the fat or the solids to a greater extent than the protein. 
Hence the proteins calculated from the fat or total solids will 
be too low and the calculated milk sugar will be too high. For 
practical purposes the limit for unskimmed milk may be set 
at 4.8 per cent, values above this being suspicious of skimmed 
milk. 

In addition to this preliminary test, the milk may be with 
certainty declared skimmed if the fat falls below 2.2 per cent, 
the solids not fat remaining above the average value of 8.5 
per cent. If the fat is above 2.2 per cent and below 3.5 per 
cent, the presence of skimmed milk may be confirmed by making 
a Kjeldahl nitrogen determination on the suspected sample and 
calculating the proteins by the factor 6.38. If the proteins 



162 AIR, WATER, AND FOOD 

exceed the fat, as stated in the preceding paragraph, the sample 
is skimmed. If, however, the fat is above 3.5 per cent, this pro- 
cedure will no longer suffice, since the proteins rarely exceed 
3.5 per cent. In these few cases, the skimming can be judged 
only from the high specific gravity, high solids not fat and cor- 
respondingly low fat. 

Specific Gravity of Milk Solids. — The specific gravity of the 
milk solids is sometimes used to show skimming. Fleisch- 
mann's formula for calculating this is 

T.S. 

x == — — — ^— — — ^— ^— -^^^— ^— — — 

„ c (100 X Gr) — 100 
ib ~ Gr 

when T.S. = the total solids and Gr the specific gravity of the 
milk. 

Example. — A sample of milk contains 12.85 per cent of milk 
solids and has a specific gravity of 1.031. Required the specific 
gravity of the milk solids. 

12.85 I2 -85 * 

x = -. r = — = 1.306. 

I2 o (100 X 1.031) - 100 12.85-3.006 

1-031 

The specific gravity of the solids of normal milk varies be- 
tween 1.25 and 1.34. It is not changed by watering the milk, 
but is increased by removing the fat or adding skimmed milk. 
A value above 1.32 is suspicious while a specific gravity of the 
milk solids above 1.40 is regarded as conclusive evidence of 
skimming. 

BUTTER 

General Statements. — Butter consists of the fat of milk, 
together with a small percentage of water, salt, and curd. The 
curd is made up principally of the casein of the milk. These 
various ingredients are present in about the following propor- 
tions : 

Fat 78.00-90.0 per cent; average, 82 per cent. 

Water 5.00-20.0 per cent; average, 12 per cent. 

Salt. 0.40-15.0 per cent; average, 5 per cent. 

Curd 0.11- 5.3 per cent; average, 1 per cent. 



ANALYTICAL METHODS 



163 



The fat consists of a mixture of the glycerides of the fatty 
acids. The characteristic feature of butter-fat is the extraor- 
dinarily high proportion of the glycerides of the soluble and 
volatile fatty acids when contrasted with other fats. 

The following may be taken as the probable composition 
of normal butter-fat : * 



Acid. 


Per cent 
Acid. 


Per cent 
Triglycerides. 


Dioxystearic 


I .OO 
32-50 

I-8 3 
38.61 

9.89 

2-57 
O.32 
O.49 
2.09 
5-45 


1.04 

33-95 
1. 91 

40.5I 
IO.44 

2-73 
0.34 
O.53 
2.32 
6.23 


Oleic 


Stearic 


Palmitic 


Myristic 


Laurie 


Capric 


Caprylic 


Caproic 


Butyric 


Total 


94-75 


IOO . OO 





According to this, the proportion of volatile acids in butter 
(butyric, caproic, caprylic and capric acids) amounts to 8.35 per 
cent. The amount of volatile acid in lard, for example, is about 
0.1 percent. 

The usual examination of butter consists in the examina- 
tion of the butter-fat, in order to detect the presence of foreign 
fats. Those commonly used for this purpose are lard, oleo- 
margarine, and sometimes butter substitutes containing cocoanut 
oil. 

The term "oleomargarine" is usually applied to a mixture 
of refined lard, "oleo oil," which is mainly the olein of beef fat, 
and cottonseed oil. Ordinarily a small proportion of butter 
is added and the product is generally churned with milk. 

A comparatively recent form of butter substitute which 
finds extensive use in some sections of the country is " process," 
or "renovated," butter. The raw material, or "stock," used for 
the manufacture of this consists of butter which cannot be sold 

* Browne: /. Am. Chem. Soc, 1899, 807. 



164 AIR, WATER, AND FOOD 

as butter either because of deterioration through rancidity or 
molding or because, through carelessness on the part of the 
makers, it possesses an unattractive appearance or flavor. The 
chief recruiting-ground for this material is the country grocery 
store. The fat, separated from the curd by melting and settling, 
is aerated to remove disagreeable odors and leave it nearly 
neutral. This is then emulsified with fresh milk which has 
been inoculated with a bacterial culture, and the whole is chilled, 
granulated, and churned. The butter is then worked and packed 
for market in the usual manner. The character of the product 
has much improved since the early days of the industry, the 
best grades now approximating the lower grades of creamery 
butter. 

The "aroma" of butter seems to be connected with the decom- 
position produced by the action of bacteria on the casein and 
the small amount of milk-sugar that is present, and not with 
any change in the fats; there is no evidence, however, that any 
unwholesome effect is produced by the aroma-giving organisms. 

The rancidity of butter-fat is generally considered to be 
due to decomposition and oxidation of the fatty acids, espe- 
cially the unsaturated ones, the amount of change depending 
on conditions of light, heat, and exposure to air. 

Analysis of Butter. — Apart from the examination of the 
butter fat to detect the addition of foreign fats, butter itself 
is often analyzed in order to determine variations in its con- 
stituents from the normal, or the addition of deleterious 
substances. 

The Federal standard for butter describes it as "the clean, 
non-rancid product made by gathering in any manner the fat 
of fresh or ripened milk or cream into a mass, which also con- 
tains a small portion of the other milk constituents, with or 
without salt, and contains not less than eighty-two and five- 
tenths (82.5) per cent of milk fat. By acts of Congress approved 
August 2, 1886, and May 9, 1902, butter may also contain added 
coloring matter." 

The determinations usually made to ascertain whether the 



ANALYTICAL METHODS 165 

butter is of standard quality are the water, fat, ash, curd, and 
salt. Of these the first four can be made on the same weighed 
sample, following in general the methods recommended by the 
Association of Official Agricultural Chemists.* 

The following method is simpler and gives results comparable 
with the official methods: 

Weigh about 2 grams of butter into a platinum Gooch cruci- 
ble, half-filled with ignited fibrous asbestos, and dry it at ioo° C. 
to constant weight. The loss in weight is the amount of water. 
Then treat the crucible repeatedly with small portions of pe- 
troleum ether, using gentle suction, and again dry it to constant 
weight. The difference between this and the preceding weight 
will be the amount of fat. Now carefully heat the crucible 
over a small flame or in a muffle until a light grayish ash is 
obtained. The loss in weight is the amount of curd, and the 
residual increase in weight over that of the crucible and asbestos 
is the ash. If desired, the salt may be washed out of the ash 
and determined by titration with silver nitrate after neutraliz- 
ing the solution with calcium carbonate. 

Notes. — If the sample for analysis is to be taken from a 
considerable quantity of butter, great care must be taken in 
sampling, because the butter is usually not homogeneous in 
composition and cannot be mixed by stirring. The best plan 
is to take a fairly large sample of 100 to 200 grams or more, 
melt it at the lowest possible temperature in a jar or wide- 
mouthed glass-stoppered bottle and mix by violent shaking. 
Then cool until sufficiently solid to prevent the separation of the 
fat and water, taking especial care to shake the sample thor- 
oughly during the cooling. 

Rapid methods for the determination of water in butter have 
been devised by Patrick f and Gray J especially for the exami- 
nation of large numbers of samples. 

Good butter should in general contain not less than the amount 

* Bur. of Chem., Bull. 107 (Rev.), p. 123. 
f /. Am. Chem. Soc., iooj, 11 26. 
% Bur. Animal hid., Circ. 100. 



1 66 AIR, WATER, AND FOOD 

of fat required by standard, not more than 2.0 per cent of curd, 
and not over 16 per cent of water. 

Salt. — If a direct determination of salt is desired, the fol- 
lowing method, although tedious, will give satisfactory results: 

Weigh 10 grams of butter -in a small beaker, add 30 c.c. of 

hot water, and when the fat is completely melted transfer the 

whole to a separatory funnel. Shake the mixture thoroughly, 

allow the fat to rise to the top, and draw off the water, taking 

care that none of the fat-globules pass the stopcock. Repeat 

the operation four times, using 30 c.c. of water each time. Make 

the washings up to 250 c.c, mix thoroughly, and titrate 25 

N 
c.c. in a six-inch porcelain dish, using — silver nitrate with 

20 

potassium chroma te as an indicator. 

Preservatives. — About 50 grams of butter are mixed with 
25 c.c. of chloroform in a separatory funnel, 100 c.c. of dilute 
(0.1 per cent) sodium carbonate solution added, and the whole 
mixed, avoiding violent shaking. After the separation of the 
layers, which may be greatly aided by a suitable centrifuge, 
the aqueous layer is examined for preservatives, especially for 
boric, benzoic and salicylic acids, by the methods described on 
pages 154 and 196. 

Colors. — No methods are described for the detection of 
colors in butter since these, being allowed, do not constitute 
an adulteration. If it be desired to test for added color in oleo- 
margarine, methods may be found in Allen's Commercial Organic 
Analysis, 4th Ed., Vol. II, or in Leach's Food Analysis. 

Examination of the Fat. — The fat is first separated from the 
other constituents of the butter so that it may be weighed out 
for the various tests. 

Directions. — Melt a piece of butter, about two cubic inches, 
in a small beaker placed on top of the water-bath so that the 
temperature shall not rise above 50 to 6o°. After about fifteen 
minutes the water, salt, and curd will have settled to the bottom. 
(A better separation may be secured by dividing the melted 
sample equally between two test-tubes and whirling them for 



ANALYTICAL METHODS 167 

3 to 4 minutes in a centrifugal machine.) Place a bit of absorb- 
ent cotton in a funnel, previously warmed, and decant off the 
clear fat through the cotton into a second beaker, taking care 
that none of the water or curd is brought upon the filter. When 
the filtered fat has cooled to about 40 place a small pipette in 
the beaker and weigh the whole. 

By means of the pipette the desired amount of fat is taken 
out, the pipette replaced in the beaker, and the whole again 
weighed. The difference in weight gives the exact amount 
of fat taken. It is a saving of time, however, if several por- 
tions are to be weighed out, to make the weights one after 
another, so that one weight will suffice for a determination. 
Weigh out thus: Two portions of 5 grams each into 250-c.c. 
round-bottomed flasks for the Reichert-Meissl method, one 
portion of 2.5 to 3 grams into a 500-c.c. beaker for Hehner's 
process, two portions of about 0.35 to 0.5 gram each into 300-c.c. 
glass-stoppered bottles for determination of the iodine value. 
In the case of the larger portions, weigh only to the nearest 
milligram. 

(1) Reichert-Meissl Number for Volatile Fatty Acids — Di- 
rections. — To the fat in the 250-c.c. flasks add 2 c.c. of strong 
caustic potash (1 : 1) and 10 c.c. of 95 per cent alcohol. Connect 
the flask with a return-flow condenser and heat on a water- 
bath so that the alcohol boils vigorously for 25 minutes. At 
the end of this time, disconnect the flask and evaporate off the 
alcohol on a boiling water-bath. After the complete removal of 
the alcohol, add 140 c.c. of recently boiled distilled water which 
has been cooled to about 50 degrees. The water should be added 
slowly, a few cubic centimeters at a time. Warm the flask on 
the water-bath until a clear solution of the soap is obtained. 
Cool the solution to about 60 degrees and add 8 c.c. of sulphuric 
acid (1 : 4) to set free the fatty acids. Drop two bits of pumice, 
about the size of a pea, into the flask, close it by a well-fitting 
cork, which is tied in with twine, and immerse it in boiling 
water until the fatty acids have melted to an oily layer floating on 
the top of the liquid. Cool the flask to about 60 degrees, re- 



1 68 AIR, WATER, AND FOOD 

move the cork, and immediately attach the flask to the 
condenser. 

Distill no c.c. into a graduated flask in as nearly thirty min- 
utes as possible. Thoroughly mix the distillate, pour the whole 
of it through a dry filter, and titrate ioo c.c. of the mixed filtrate 

N 
with — sodium hydroxide, using phenolphthalein as an indicator. 
10 

Multiply the number of cubic centimeters of alkali used by 

eleven-tenths, and correct the reading also for any weight of 

fat greater or less than 5 grams. 

For example, if 5.3 grams of butter-fat are used, and 100 c.c. 

N 
of the distillate require 27.4 c.c. of — NaOH, no c.c. would re- 

10 

quire 27.4 Xjj = 30.14 c.c. Then 5.3 : 30.14 = 5 : x. x = 

28.4. x is the Reichert-Meissl number. 

Notes. — The Reichert-Meissl number for genuine butter 
varies from 24 to 34; the average usually taken is 28.8. 

Cocoanut oil gives a value of 6-8; other edible fats and oils 
have a value usually less than 1. 

Cocoanut oil is used, to some extent, as a substitute for butter 
in confections and crackers, in cooking fats, and also in cocoa- 
butter substitutes. Its presence is indicated by the Reichert- 
Meissl number taken in connection with the saponification value, 
that is, the number of milligrams of potassium hydroxide re- 
quired to saponify one gram of the fat. (For a description of 
the method of determining this see Lewkowitsch: Oils, Fats 
and Waxes; or Gill: A Short Handbook of Oil Analysis.) The 
Reichert-Meissl number is higher in butter fat than in cocoanut 
oil, while the saponification value is lower. In pure butter fat 
the value of the expression: 

Saponification value — (Reichert-Meissl number — 200) varies 
from 3.4 to 4.1; in pure cocoanut oil, it runs from 47 to 50.7.* 

Another method of value in showing the presence of cocoanut 
oil is the determination of the Polenske number f which repre- 

* Juckenack and Pasternack: Ztschr. Nahr. Genussm., 7, 1904, 193. 
f Polenske: Ztschr. Nahr. Genussm., 1904, 273. 



ANALYTICAL METHODS 169 

sents the volatile fatty acids insoluble in water. This value for 
butter is from 1 to 3; for cocoanut oil, from 16 to 18. Details 
of the procedure, which it requires some experience to carry out 
successfully, may be found in the original paper or in Leach's 
Food Analysis, 3d ed., page 483. 

The reactions involved in the Reichert-Meissl method may be 
simply explained as follows: 

When the fat is treated with potash it is decomposed, the 
glycerine being set free, and the potassium salts of the fatty 
acids, that is to say, the potassium soaps, are formed. Hence 
the process is called saponification. For butyric acid the re- 
action may be expressed, 

C 3 H5(C 3 H 7 COO)3 + 3 KOH = 3 C 3 H 7 COOK + C3H 5 (OH) 3 . 

The alcohol is used to dissolve the fat. But at the moment 
the butyric acid is set free it tends to combine with the alcohol to 
form a volatile ether: 

C 3 H 7 COOH + C2H5OH = C 3 H 7 COOC 2 H 5 + H 2 0. 

The object of the return-flow condenser is to prevent the escape 
of this volatile ether and to allow of its complete saponification. 

If the water used to dissolve the soap is added too rapidly, 
the soap may be decomposed with the liberation of the fatty 
acids: C 3 H 7 COOK + H 2 = C 3 H 7 COOH + KOH. 

The fatty acids are set free at the proper time by means of 
sulphuric acid, and the volatile acids distilled off and titrated. 
The pumice is added to prevent explosive boiling. 

The whole of the volatile acids do not pass over into the dis- 
tillate, but only a part, the amount depending upon the rate of 
distillation and the volume of the distillate. Hence, in order to 
get uniform results, it is necessary to follow the prescribed pro- 
cedure with great care. 

In Great Britain all determinations of the Reichert-Meissl 
number, which are likely to lead to prosecutions under the Mar- 
garine Act, must be made in a specified apparatus, the dimensions 
of which are definitely stated and the procedure exactly defined.* 
* Analyst, 25, 1900, 309. 



170 AIR, WATER, AND FOOD 

Some of the errors in the Reichert-Meissl method may be 
avoided, and the process materially shortened by carrying out 
the saponification with glycerol and caustic soda as recommended 
by Leffman and Beam.* The method is as follows: 

Weigh 5 grams of the fat into a 250-c.c. round-bottomed 
flask and add 20 c.c. of glycerol-soda solution.! Hold the flask 
with tongs, and heat it directly over a flame until foaming ceases 
and the mixture becomes perfectly clear, which ordinarily re- 
quires about five minutes. Add to the clear soap solution 135 
c.c. of water, adding it at first in very small portions to prevent 
foaming. Finally add the pumice and sulphuric acid, as in the 
Reichert-Meissl method, and distill without previous melting of 
the fatty acids. 

(2) Hehner's Method for Direct Determination of the Fixed 
Fatty Acids. — Directions. — To the portion of 2.5 grams 
weighed out into the 500-c.c. beaker add 1 c.c. of caustic potash 
and 20 c.c. of 95 per cent alcohol. Cover the beaker with a 
watch-glass and heat it on the water-bath until the liquid is 
clear and homogeneous. As it is not essential to prevent the 
escape of the volatile acids, the use of a return-flow condenser 
is not necessary. Evaporate off the alcohol on the water-bath 
and dissolve the soap in about 400 c.c. of warm distilled water. 
When the soap is completely dissolved, add 10 c.c. of hydro- 
chloric acid (sp. gr. 1.12), and heat the beaker in the water- 
bath almost to boiling until the clear oil floats. Meanwhile, dry 
and weigh a thick filter in a small covered beaker. Allow the 
solution to cool until the fat forms a solid cake on top; filter the 
clear liquid and finally bring the solid fats upon the weighed 
filter. Wash the beaker and fat thoroughly with cold water, 
then wash out the fat adhering to the beaker with boiling water, 
which is poured through the filter, taking care that the filter is 
never more than two-thirds full. If the filter paper is of good 
texture and thoroughly wet beforehand, it will retain the fatty 
acids completely. If, however, oily particles are noticed in the 

* Analyst, 1891, 153. 

t 20 c.c. of 50 per cent caustic soda solution to 180 c.c. of glycerol. 



ANALYTICAL METHODS 171 

filtrate, cool it by adding pieces of ice, remove the solidified par- 
ticles with a glass rod and transfer them to the filter. Cool the 
funnel by plunging it into cold water, remove the filter, place it 
in the weighing-beaker, and dry it at ioo° to constant weight. 
The fat should be heated about an hour at first, then for periods 
of about thirty minutes, until the weight is constant within 
2 mgs. 

Notes. — 87.5 per cent is usually taken as the proportion of 
fixed fatty acids in butter-fat; 88 and 89 per cent have been 
frequently found. All other fats yield from 95 to 96 per cent 
of insoluble fatty acids. 

(3) Determination of Iodine Value. — This method is based 
on the fact that certain of the fatty acids, notably the " unsatu- 
rated acids," as oleic acid, G7H33COOH, take up the halogens 
with the formation of addition products. 

Directions. — Dissolve the fat in the 300-c.c. bottles in 10 c.c. 

of chloroform. Add 30 c.c. of the iodine solution from a pipette 

or glass-stoppered burette, and allow the bottles to stand with 

occasional shaking for thirty minutes. Add 10 c.c. of 20 per 

cent potassium iodide solution and mix thoroughly, then 100 c.c. 

N 
of distilled water, and titrate the excess of iodine with — sodium 

10 

thiosulphate until the solution is faintly yellow. Add 2 to 3 c.c. 
of starch solution and titrate to the disappearance of the blue 
color. Toward the end of the titration shake the bottle vigor- 
ously so that any iodine remaining in the chloroform may react 
with the thiosulphate. Calculate the result in grams of iodine 
absorbed by 100 grams of fat. This is called the Iodine 
Number, or Iodine Value. 

At the time of making the determination carry out two 
" blanks" in exactly the same way except that no fat is used. 

Standardization of the Thiosulphate Solution. — As this is not 
permanent, its strength should be determined by means of the 
standard potassium bichromate solution, 1 c.c. of which is 
equivalent to 0.01 gram of iodine. 

Measure 20 c.c. of the potassium bichromate from a pipette 



172 AIR, WATER, AND FOOD 

into an Erlenmeyer flask. Add 5 c.c. of potassium iodide, 100 
ex. of water, and 5 c.c. of strong hydrochloric acid. Titrate the 
liberated iodine with the thiosulphate solution until the color 
has almost disappeared, then add starch solution and continue 
the titration until the blue color disappears, leaving the sea- 
green color of the chromium chloride. The iodine is liberated in 
accordance with the following equation : 
K 2 Cr 2 7 + 14 HC1 + 6 KI = 8 KC1 + 2 CrCl 3 + 7 H 2 + 6 I. 

Calculation of Results. — Example. — From the standardi- 
zation, 

16.07 cx - thiosulphate = 20 c.c. bichromate = 0.200 gram I; 
1 c.c. thiosulphate = 0.0125 gram I. 

Also, from blank, 

30 c.c. iodine solution = 63.60 c.c. thiosulphate. 

If 44.85 c.c. thiosulphate were used to titrate the excess of 
free iodine, 63.60 — 44.85 = 18.75 cx - * s the amount of thio- 
sulphate equivalent to the iodine combined with the fat. If 
0.3271 gram of fat were used, since 1 c.c. thiosulphate is equiva- 

i £ • j- I ^-75 X 0.0125 w 

lent to 0.012 s gram free iodine, — — X 100 = 71.66 

0.3271 

grams of iodine combined with 100 grams fat. 

Notes. — The Iodine Number of butter fat varies between 26 
and 38; of oleomargarine, between 60 and 75; of lard, between 
46 and 70; of cottonseed oil, from 106 to no; and of cocoanut 
oil, between 8 and 9.5. 

The products formed by the action of iodine on the fats are 
mainly addition products with a slight proportion of substituted 
bodies. Thus the unsaturated olein, 

(C 17 H33COO) 3 C 3 H5, 

takes up six atoms of iodine, forming an addition product, 
di-iodo-stearin, (Ci7H33l2COO) 3 C 3 H5. 

The method in general use for determining the iodine value 
of fats and oils has been that of Baron Hiibl,* an alcoholic solu- 

* Ding. Poly. J., 253, 281; /. Soc. Chem. Ind., 3, 1884, 641. 



ANALYTICAL METHODS 1 73 

tion of iodine and mercuric chloride being used as the reagent. 
The method here described, due to Hanus,* has the advantage 
that the solutions keep better, remaining practically unchanged 
for several months, and that the action is about sixteen times 
as rapid. For the fats and for oils with low iodine values, the 
results are very close to the figures obtained by the Hiibl proc- 
ess. If it is desired to carry out the determination by the 
older method, directions can be found in any standard work on 
the analysis of oils. 

It should be noted that the " iodine solution" is a solution of 
iodine bromide in glacial acetic acid, hence great care should be 
taken that there is no change in temperature between the time 
of measuring the solution of iodine for the blanks and for the de- 
terminations, since the high coefficient of expansion of acetic 
acid may cause a material error. 

Further, the amount of fat taken for the analysis should be 
such that only a portion of the iodine is absorbed, 60 to 70 per 
cent being in excess. Care should also be taken to avoid vigor- 
ous shaking of the glass-stoppered bottles until near the end of 
the titration to prevent loss of iodine from the stopper. 

(4) Refractive Index. — The determination of the refractive 
index is especially valuable in the examination of butter, and for 
that matter, in food analysis in general, owing to the rapidity 
with which the test can be made and the fact that so little of the 
substance is required. Various forms of refractometers are 
used for the purpose, a fairly complete description of which 
will be found in some of the larger works, such as Leach: Food 
Inspection and Analysis; or Vaubel: Quantitative Bestimmung 
organischer Verbindungen. The instrument having the widest 
range is the Abbe refractometer, in which the index of re- 
fraction is determined by measuring the total reflection pro- 
duced by a very thin layer of the melted fat, placed between two 
prisms of flint glass. This instrument, fitted with water- jacketed 
prisms, is shown in Fig. 13. 

Directions. — Revolve the whole instrument on the axis b until 

* Ztschr. Unters. Nahr. u. Genussm., 4, 1901, 913. 



174 



AIR, WATER, AND FOOD 



it reaches the stop provided, then open the prism casing AB by 
giving the pin v a half-turn (to the right). Be sure that the 
prism surfaces are clean. If not, clean them carefully with a soft 
cloth and a little alcohol. Place a few drops of the melted 




Fig. 13. 



sample directly on the surface of the prism and clamp the two 
together again by turning the pin v in the opposite direction. 
Now turn the instrument back (toward the observer) as far as 
possible and bring the "critical line" into the field of vision of 
the telescope. This is done by holding the sector 5 firmly with 
the hand and revolving the double prism by means of the alidade 
/ until the field is divided into a light and a dark portion. If 



ANALYTICAL METHODS 



175 




the line is not sharp focus the ocular of the telescope. If it is 
colored it is due to dispersion of the light by the liquid and 
should be corrected by revolving the compensator T by the 
milled screw M. The correction is made by a system of two re- 
volving Amici prisms in the lower part of the telescope. Adjust 
the critical line so that it falls on the intersection of the cross 
hairs of the telescope. Observe the temperature by the ther- 
mometer inserted in 
the prism casing. In 
the case of solid fats, 
a sufficiently high 
temperature should 
be maintained by a 
current of war m 
water to keep the 
sample well above its 
melting point. A 
temperature of 30 to 
40 C. is usually suffi- 
cient. Do not let the temperature rise above 70 or the prisms 
may be injured. Read the index of refraction directly through 
the small lens L, estimating the fourth decimal. Calculate the 
value for the refractive index at 25 C. 

Notes. — The principle on which the Abbe refractometer is 
based will, perhaps, be more clearly understood by reference to 
Fig. 14. 

Let AB be the surface of separation between two media, of 
which the upper is the rarer, and let a beam of light pass through 
in the direction 10. It will be seen that as the light passes from 
the denser to the rarer medium, the angle of refraction r will be 
greater than the angle of incidence i. If the angle of incidence 
be increased, then for a certain incident angle, the angle of re- 
fraction will become 90 , that is, the refracted ray will coincide 
with the dividing surface. For incident rays striking the sur- 
face at a greater angle than this, the light will be totally reflected 
and there will be no refracted ray. The angle of incidence at 



Fig. 14. 



176 



AIR, WATER, AND FOOD 



which this occurs is known as the critical angle, 
sin i 



Then since n 



sin r 



sin 1 



sin 1 



sin 



at the critical angle n 

sin 90 1 

That is, in passing from a denser to a rarer medium, the index of 

refraction is equal to the sine of the angle of incidence for the 

border line of total re- 



flection. 

In the Abbe refrac- 
tometer the refractive 
index of the liquid is 
determined by measur- 
ing the critical angle 
for light passing into 
it from a glass prism of 
higher refractive index. The sine of 
this angle is the index of refraction 
of the liquid, referred to glass, and 
this multiplied by the refractive in- 
dex of the glass gives the index of 
refraction of the liquid referred to air. 
The divisions on the scale are pro- 
portional to the sines of the angles 
of incidence for total reflection, multi- 
plied by 1.75, the refractive index of 
the prism and, therefore, give directly 
the refractive index of the substance 
examined. Since the light must pass 
from the denser to the rarer medium, 
it is evident that the instrument is FlG - I S- 

limited to liquids whose refractive indices are less than 1.75. 

Fig. 15, from Browne's Handbook of Sugar Analysis, illus- 
trates diagrammatically the passage of light through the in- 
strument. The heavy line represents the border line of total 
reflection, the light striking the surface AB at a less angle being 




ANALYTICAL METHODS 



177 



refracted, and illuminating the field of the telescope. The rays 
which fall upon the surface at a greater angle are totally reflected, 
leaving the corresponding portion of the telescopic field dark. 

The index of refraction decreases with rising temperature. 
With the common oils and fats, the change for each degree is 
very nearly a constant, amounting to 0.000365. Leach and 
Lythgoe * have devised a sliding scale by means of which the 
temperature correction may be readily made without reference to 
tables. 

The values of tin for genuine butter lie between 1.4590 and 
1.4620; for oleomargarine the values range from 1.4650 to 
1.4700. 

The correctness of the instrument should be tested by the 
"test-plate" which comes with it, cementing it to the prism 
with monobromnaphthalene, or the testing may be done more 
conveniently with distilled water. The refractive index of water 
at ordinary temperatures is given below: 



Tempera- 


Refractive 


Tempera- 


Refractive 


ture, °c. 


Index. 


ture, °C. 


Index. 


18 


1-3332 


23 


1-3327 


19 


I 3331 


24 


I.3326 


20 


1-3330 


25 


I-332S 


21 


1-3329 


26 


1-3324 


22 


1-3328 


27 


1-3323 



Special Tests for Distinguishing Renovated Butter. — Spoon 
Test or "Foam" Test. — Melt a piece of the sample as large as a 
small chestnut in an ordinary tablespoon or a small tin dish. 
Use a small flame and stir the melting fat with a splinter of wood 
(such as a match) . Then increase the heat so that the fat shall 
boil briskly, and stir thoroughly, not neglecting the outer edges, 
several times during the boiling. 

Oleomargarine and renovated butter boil noisily, usually 
sputtering like a mixture of grease and water when boiled, and 

* /. Am. Chem. Soc, 1904, 1193. 



178 AIR, WATER, AND FOOD 

produce little or no foam. Genuine butter usually boils with 
much less noise and produces an abundance of foam, often rising 
over the sides of the dish or spoon when the latter is removed 
temporarily from the flame. The difference in regard to the 
foam is very marked. 

Note also the appearance of the particles of curd after the 
boiling. With genuine butter these will be very small and 
finely divided, hardly noticeable in fact, while with oleomargarine 
and renovated butter the curd gathers in much larger masses 
or lumps. 

Notes. — This simple method is of value for giving a quick 
decision regarding a sample, and is especially useful for the 
detection of renovated butter. The differences in the compo- 
sition of butter-fat brought about by renovation are so slight 
that chemical methods are here of no avail. 

The spoon test, however, will distinguish in the great majority 
of cases between genuine butter on the one hand and oleo- 
margarine and renovated butter on the other; the index of 
refraction or the chemical methods just described readily dis- 
tinguish between the two latter. 

In genuine butter the curd is somewhat different in compo- 
sition from that of renovated butter or oleomargarine in that it 
consists largely of the milk proteins that are insoluble in water, 
and hence accompany the separated cream. The curd of reno- 
vated butter or oleomargarine, on the other hand, comes from 
the proteins of the milk added directly in the process of manu- 
facture, and consists mainly of coagulated casein. Hence its 
different appearance in the test. 

The crackling and sputtering of the fat in the case of oleo- 
margarine and renovated butter are due to the fact that in the 
process of manufacture of these the melted fat is sprayed into 
ice-water, and the cooled particles enclose some water. 

Microscopic Examination. — Pure, fresh butter is not ordi- 
narily crystalline in structure. Butter which has been melted, 
however, and fats which have been liquefied and allowed to cool 
slowly show a distinct crystalline structure, especially by polar- 



ANALYTICAL METHODS 1 79 

ized light. If only fresh butter were sold, and all adulterants 
had been previously melted and slowly cooled, this method would 
be all that would be necessary for the detection of adulteration. 
As it is, however, it is most useful in making comparative exami- 
nations of samples which have been subjected to the same 
conditions. 

About the most that can be said is that if a small bit, about 
the size of a pin-head, of the fresh, unmelted sample, is taken 
from the center of the mass and pressed out on a slide by gentle 
pressure on the cover glass, it ought to show a fairly uniform 
field if examined with a one-sixth objective, using polarized 
light and a selenite plate. Other fats melted and cooled, and 
mixed with butter, generally show a crystalline structure and a 
variegated color with the selenite plate. 

In the case of renovated butter, however, there is a distinct 
difference to be noted in the appearance of the field. With 
genuine butter the field is much more clear and free from opaque 
masses of curd than with renovated butter. When the slide is 
examined by reflected light, turning the mirror so as not to pass 
light through the slide, these opaque masses in the case of reno- 
vated butter show strikingly as white masses against a dark 
background. 

CEREALS 

The great importance of cereal food in the diet may be 
gathered from the fact that dietary studies among a large num- 
ber of American families have shown that about three-fourths 
of the vegetable protein, one-half of the carbohydrates, and 
seven-eighths of the vegetable fat are supplied by the cereals. 
The reason for such an extensive use of the cereals lies in the 
fact that, besides being cheap and easily grown, they contain 
unusually large proportions of nutriment with a very small pro- 
portion of refuse. They are readily prepared for the table, are 
palatable and digestible. In distinction from the two classes of 
food materials already considered, they are in a dry form, and 
not liable to rapid change by micro-organisms. 



180 AIR, WATER, AND FOOD 

Prepared breakfast foods may be taken as typical and inter- 
esting cereal products, and since many of these are somewhat 
modified from their original composition by cooking or by 
treatment with malt, the form in which the carbohydrates are 
present is of almost equal importance with the determination of 
nitrogen. 

The fact that in the breakfast cereals the process of manu- 
facture has in no way increased their actual food value over the 
grains from which they were prepared, as pointed out in Chapter 
VIII, is emphasized by the figures in the accompanying table in 
which some of the most widely-used preparations are compared 
with the original grains. It will be observed that practically the 
only change is in the solubility of the carbohydrates, the starch 
being changed in part to dextrin. In the case of the malted food, 
the change may go even farther, and a greater or less amount of 
reducing sugar, principally maltose, be formed. 

Moisture. — Directions. — Spread about 2 grams of the 
finely ground material in a thin layer on a watch-glass and dry 
it in the oven at ioo° C. for five hours. On account of the 
ready absorption of moisture by the dried sample, the use of 
clipped watch-glasses will be found advantageous. 

Note. — With some substances drying in a current of hydro- 
gen or some inert gas may be necessary, but for most cereals the 
method given will be found satisfactory. 

Ash. — Directions. — Weigh about 2 grams into a platinum 
dish, such as is used for the determination of solids in milk, and 
char it carefully. Ignite at a very low red heat until the ash is 
white, preferably in a mufHe. 

Notes. — If a white ash cannot be obtained in this manner, 
exhaust the charred mass with water, collect the insoluble 
residue on a filter, burn it, add this ash to the residue from the 
evaporation of the aqueous extract and heat the whole at a low 
red heat until the ash is white. 

Some cereals, such as whole wheat and barley, will act de- 
structively on platinum dishes, on account of the phosphates 
present, but can be ignited safely in platinum in the mufHe. 



ANALYTICAL METHODS 



181 



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1 82 AIR, WATER, AND FOOD 

Fat: Ether Extract. — Directions. — Place the residue from 
the determination of moisture, as described above, in a porous 
paper cup and extract it with pure anhydrous ether for sixteen 
hours, using the Soxhlet extractor and electric heater as de- 
scribed on page 141. Evaporate off the ether and dry the 
residual fat at the temperature of boiling water to constant 
weight. 

Note. — The ether extract of cereals is not pure fat but may 
contain more or less coloring matter or resins. Petroleum ether 
can be used for the extraction, giving results not essentially 
different from those obtained with anhydrous ethyl ether. 

Total Protein: Determination of Nitrogen by the Kjeldahl 
Process.* — This method is based upon the decomposition of 
the nitrogenous material by boiling with strong sulphuric acid. 
The carbon and hydrogen are oxidized to carbon dioxide and 
water, a portion of the sulphuric acid being reduced to sulphur 
dioxide. The nitrogen is left as ammonium sulphate from 
which the ammonia is liberated by potash or soda and distilled 
into a known excess of standard acid. The time of digestion 
can be materially shortened by the use of substances like mer- 
cury or potassium sulphate which assist the oxidation or raise 
the boiling-point of the acid. 

Directions. — Transfer about 0.5 gram of the finely divided 
substance from a weighing-tube to a pear-shaped digestion flask, 
add 10 c.c. of concentrated sulphuric acid free from nitrogen, 
and 0.2 gram (three small drops) of metallic mercury. Place a 
small funnel in the neck of the flask, which should be sup- 
ported in an inclined position on wire gauze and heated with a 
small flame until frothing has ceased and the liquid boils quietly. 
Then increase the heat and boil the solution for at least an 
hour after it becomes colorless. Allow the flask to cool for a 
minute or two, and add a few crystals of potassium permanganate 
until the liquid has acquired a slight green or purple color. 

N 
Measure 25 c.c. of — acid from a burette into a 300-c.c. 
10 

* Ztschr. anal. Chetn., 22, 1883, 366. 



ANALYTICAL METHODS 183 

Erlenmeyer flask and place the condenser-tip beneath the 

surface of the liquid, adding a little water, if necessary, to seal 

it. 

Transfer the digestate with several small portions of distilled 

water to the distilling flask of the apparatus, add 20 c.c. of 

potassium sulphide solution, and connect the flask with the 

condenser. Add 50 c.c. of caustic potash through the separa- 

tory funnel, and distill off the ammonia by steam. When 200 

c.c. have distilled over, remove the collecting-flask, after rinsing 

off the condenser-tip with distilled water, and titrate the excess 

N 
of acid with — sodium hydroxide, using methyl orange or 
10 

cochineal as indicator. If using new reagents, a blank deter- 
mination should be made with 0.5 gram of cane-sugar in order 
to reduce any nitrates present which might otherwise escape 
detection. 

Notes. — The temperature during the digestion must be 
maintained at or near the boiling-point of the acid, since at a 
lower temperature the formation of ammonia is incomplete. 

In some cases, the potassium permanganate is necessary to 
insure the complete conversion of the nitrogenous bodies into 
ammonia, although it is probable that its use is unnecessary in 
the majority of analyses. 

The addition of potassium sulphide before distilling is to pre- 
cipitate the mercury and thus prevent the formation of non- 
volatile mercur-ammonium compounds. 

The Kjeldahl process in the form outlined above is not ap- 
plicable to the determination of nitrogen in the form of nitrates. 
In order to render it of more general application various modi- 
fications of the method have been proposed, the one generally 
used in this country being that suggested by ScovelL* In this 
method salicylic acid is used with the sulphuric acid, being con- 
verted by the nitrate into nitro-phenol. By the use of sodium 
thiosulphate or zinc-dust this is reduced to amido-phenol. The 
amido-phenol is transformed into ammonium sulphate by the 

* U. S. Dept. Agr., Bull. 16, 1887, 51. 



184 AIR, WATER, AND FOOD 

heating with sulphuric acid, the use of mercury being absolutely 
necessary in this case to secure the complete transformation. It 
is true also that certain other nitrogenous bodies, notably the 
alkaloids and certain organic bases, do not yield all their nitro- 
gen to the Kjeldahl process without modifications which com- 
plicate the method. For a discussion of the efficiency of these 
various modifications the student is referred to a paper by 
Sherman and Falk.* In the case of cereals, however, and with 
the majority of food products, the simpler method outlined will 
prove entirely satisfactory. 

The per cent of proteids may be found by multiplying the 
per cent of nitrogen by an appropriate factor, the one in general 
use being 6.25. Recent work has shown, however, that most 
of the proteids of cereals contain more than 16 per cent of 
nitrogen, so that the factor 6.25 gives results that are too high. 
Because all the older work was calculated on this factor, it is 
still generally used, nevertheless. 

Kjeldahl-Gunning Method. — The Gunning method can be 
used in all cases where the Kjeldahl- Wilfarth modification, just 
described, is employed, and in some ways it is simpler. 

The digestion and distillation are carried out as described on 
page 182, using the same amount of sample, together with 20 c.c. 
of concentrated sulphuric acid and 10 grams of powdered potas- 
sium sulphate. No mercury and, consequently, no potassium 
sulphide is used. 100 c.c. of the potash should be added in- 
stead of 50. 

Note. — The potassium sulphate is added to raise the boiling 
point of the sulphuric acid and thus shorten the time required 
for the digestion. 

Carbohydrates. — The total carbohydrates, often stated in 
analyses as " nitrogen-free extract," may be readily obtained by 
subtracting from 100 the sum of the percentages of the other 
constituents, viz., moisture, ash, ether extract, and nitrogenous 
bodies. In many cases, however, especially with the cooked or 
treated cereals and with such classes of cereal preparations as 

* /. Am. Chem. Soc, 1904, 1469. 



ANALYTICAL METHODS 185 

infant or invalid foods, a further study of the carbohydrates is 
desirable. These are made up of two general classes : (a) soluble 
carbohydrates, including sugars, as sucrose, dextrose and maltose, 
dextrin and soluble starch, by the latter term being meant starch 
which is soluble in water but still gives the characteristic blue 
color with iodine, in distinction from some of the more com- 
pletely broken-down forms like dextrin, which no longer give 
blue or purple colors with iodine; (b) insoluble carbohydrates, in- 
cluding starch, pentosans, lignin bodies, and cellulose. The 
three latter occur chiefly in the husk or envelope of the grain 
or in the woody fiber of the plant. The pentosans or gums are 
distinguished from one another by the formation of specific 
sugars upon hydrolysis with acids. For ordinary analytical 
purposes it is sufficient to determine the lignin and cellulose to- 
gether as " crude fiber." Since the exact procedure to be fol- 
lowed in the determination of the carbohydrates varies largely 
with each specific case, only a general outline can be presented 
here. 

Sugars. — The finely ground material, previously dried and 
extracted with ether for the removal of crude fat, is extracted 
with 85 per cent alcohol. In the extract the reducing sugars 
may be determined by means of Fehling's solution as described 
on page 145, and the sucrose determined in the same way after 
inversion with hydrochloric acid. 

Dextrin and Soluble Starch. — The residue from the extrac- 
tion of the sugars is treated for eighteen to twenty-four hours 
with water at laboratory temperature with frequent agitation, 
made up to definite volume, and filtered. This may be tested 
with iodine, and if no blue color is produced, evaporated to small 
volume, and the dextrin converted to dextrose by dilute hydro- 
chloric acid and determined by Fehling's solution. In some few 
cases, however, a blue color with iodine may indicate the presence 
of soluble starch, in which case an aliquot part of the filtrate may 
be treated with an excess of barium hydroxide to precipitate 
the starch. In the filtrate from this precipitate the dextrin is 
determined by inversion and copper reduction as before. The 



186 AIR, WATER, AND FOOD 

difference between the dextrin thus found and the first deter- 
mination gives the soluble starch. 

Starch. — This may be determined in the residue insoluble in 
cold water by digesting it with malt extract, and determining the 
dextrose after hydrolysis with dilute acid. It is more common, 
however, to determine the starch and other insoluble carbo- 
hydrates directly on the original material. The methods for the 
determination of starch vary with the condition in which the 
starch is found. In the case of nearly pure starch it may be 
converted into dextrose by boiling with dilute acid, the dextrose 
being then determined by Fehling's solution in the usual way. 
Hot acids, however, cannot be used to convert starch in the 
natural state, as it is found in cereals, because other carbohydrate 
bodies, especially the pentosans, become soluble under these 
conditions and the results are too high. In such cases, the 
starch is brought into solution by treatment with diastase or by 
heating with water under pressure. The results obtained by 
direct acid hydrolysis, however, in cases where the highest 
accuracy is not required, may be sufficient and the method is 
much quicker and easier of execution than the digestion with 
diastase. 

Direct Acid Hydrolysis. — Directions. — Weigh out from 2 to 
5 grams of the sample, depending upon the amount of starch 
present, and wash on a filter with five successive portions of 
10 c.c. each of ether. Allow the ether to evaporate from the 
residue and then wash it with 10 per cent alcohol until free from 
soluble carbohydrates. 150 c.c. of the dilute alcohol is generally 
sufficient, but if much reducing sugar or dextrin is present, as 
may be the case with malted cereals, more will be necessary. 
Wash the residue from the filter with 200 c.c. of water into a 
500 c.c. graduated flask, add 20 c.c. of hydrochloric acid, sp. gr. 
1. 1 2 5, place a funnel in the neck of the flask to retard evapo- 
ration, and heat in a boiling water-bath for two and one-half 
hours. Cool, nearly neutralize with sodium hydroxide and 
make up to 500 c.c. Filter, and determine dextrose in an 
aliquot portion, 25 or 50 c.c. of the filtrate, using the method de- 



ANALYTICAL METHODS 187 

scribed on page 145. Convert dextrose to starch by the factor 
0.9. 

Note. — The washing to remove soluble carbohydrates is per- 
formed with dilute alcohol rather than with water, because the 
former is less likely to carry starch granules through the paper. 
The sugar solution when added to the Fehling's solution should 
be clear and only faintly acid. It should, in general, contain 
not more than 0.5 per cent of reducing sugar. 

Determination with Diastase. — Directions. — Treat 2 to 5 
grams of the sample with ether and dilute alcohol, as in the 
previous method, and wash the residue into a 250-c.c. flask 
with 50 c.c. of water. Heat slowly to boiling, or immerse the 
flask in boiling water, until the starch gelatinizes, stirring con- 
stantly to prevent the formation of lumps. Cool to 55 C, add 
20 to 40 c.c. of malt extract, and keep the solution within two 
degrees of the stated temperature for an hour or until the solu- 
tion no longer gives the starch reaction with iodine under the 
microscope. In either case, heat the solution again to boiling 
to gelatinize any remaining starch granules, test again and if 
starch is found, cool to 55 C, and treat as before, using a 
fresh portion of malt extract. Continue this treatment until, 
when carefully examined under the microscope, a drop of the 
solution fails to give the iodine reaction for starch. Cool, 
make up to 250 c.c. and filter through a dry filter. Transfer 
200 c.c. of the nitrate to a 500-c.c. graduated flask, add 20 c.c. 
of hydrochloric acid, sp. gr. 1.125, and carry out the determina- 
tion as described in the preceding method. 

A blank determination must be carried through, using 50 c.c. 
of water and exactly the same amount of malt extract as used in 
the regular procedure, in order to correct for the cupric reducing 
power of the malt extract. 

Malt Extract. — Treat 40 grams of fresh coarsely ground malt 
several hours with 200 c.c. of water, shaking occasionally. 
Filter and add a few drops of chloroform to prevent the growth 
of molds. 

Notes. — The action of the diastase on the gelatinized starch 



1 88 AIR, WATER, AND FOOD 

is to convert it into maltose and dextrin, that is, into soluble 
bodies that can be separated by filtration from the pentosans 
and other carbohydrates that give the high results in the direct 
acid method. By the action of acid (hydrolysis) the maltose and 
dextrin are converted to dextrose. 

The determination should, if possible, be carried through 
without interruption. In case this cannot be done, salicylic acid 
may be used to prevent fermentation, not adding it, however, 
until after the digestion with diastase. 

If the malt itself is not readily procurable, certain forms of 
prepared diastase are on the market and may be found more 
convenient either for analytical use or for purposes of illustration. 
When possible, however, it is preferable to use the freshly pre- 
pared malt extract, as the prepared diastase, made at different 
times and from separate portions of malt, may show great differ- 
ences in hydrolytic power. 

It is sometimes convenient to use freshly collected saliva, 
this being free from carbohydrate. In this case, the digestion 
should be carried out at 38 C. instead of 55 C. 

Crude Fibre. — The Weende method, the one adopted by the 
Association of Official Agricultural Chemists, is based on the 
assumption that the starch and other digestible carbohydrates 
and protein will be removed from the cereal by successive di- 
gestion at a boiling temperature with acid and alkali of a definite 
strength. The complex body thus obtained is not a definite 
chemical compound, but may be considered as being composed 
largely of cellulose. 

Use 2 grams of the finely-ground sample and wash on a filter 
with 5 portions of 10 c.c. each of ether. (The residue from the 
determination of " ether extract" can be used if desired.) 

Transfer the washed material to a 500-c.c. Erlenmeyer flask, 
add 200 c.c. of boiling 1.25 per cent sulphuric acid, place a 
funnel in the neck of the flask and boil gently for 30 minutes. 
Filter on a ribbed filter and wash with several portions of boiling 
water. Transfer the precipitate by means of 200 c.c. of boiling 
1.25 per cent sodium hydroxide in a small wash-bottle to the 



ANALYTICAL METHODS 189 

same 500-c.c. Erlenmeyer flask, and boil again gently for 30 
minutes. 

Filter on ignited asbestos in a Gooch crucible, wash with 
boiling water until free from alkali, then with 10 c.c. of alcohol, 
and finally with 10 c.c. of ether. Dry at the temperature of 
boiling water to constant weight. Ignite carefully at first, then 
at a low red heat until the organic matter is destroyed. Calcu- 
late the loss on ignition as " crude fibre." 

Note. — The filtration will be found to proceed fairly rapidly 
if the solution is filtered hot and care is taken to keep the residue 
from the filter as long as possible. 

The sulphuric acid and sodium hydroxide should be carefully 
prepared and the strength determined by titration. 

Examination of Malted Cereals. — The relation of the carbo- 
hydrates in a malted cereal, which ordinarily consist of maltose, 
dextrin and starch, may be readily learned by the following 
simple analytical scheme, due to Sherman.* 

Directions. — Mix 5 grams of the ground sample with 125 c.c. 
of cold water in a 250-c.c. graduated flask and allow it to stand 
at room temperature for an hour, shaking frequently. Make 
up to the mark, mix and filter through a dry filter. Determine 
the reducing sugar in 25 c.c. of the filtrate as described on page 
145, and calculate as maltose in the original sample. Measure 
50 c.c. of the same filtrate into a 100-c.c. flask, add 5 c.c. of 
hydrochloric acid (sp. gr. 1.12), and hydrolyze as directed on 
page 186. Filter and determine the dextrose in the filtrate as 
on page 145. Subtract the amount due to maltose and calculate 
the remainder to dextrin by multiplying by 0.9. 

Treat another portion of the original sample as described un- 
der the determination of starch by acid hydrolysis, page 186, 
without, however, extracting the soluble carbohydrates. From 
the dextrose found subtract that given by dextrin and maltose 
and calculate the remainder to starch. 

Notes. — The presence of undissolved material in the flask 
when diluted to volume renders the result somewhat inaccurate, 

* Methods of Organic Analysis, 2d Ed., p. 341. 



190 AIR, WATER, AND FOOD 

and the possible presence of other reducing sugars than maltose 
introduces error, but the results are sufficiently close for com- 
parative tests. 

Examination of Fermented Liquors 
wine 

General Statements. — The object of a wine analysis is ordi- 
narily to determine whether or not a wine is pure and un- 
adulterated, or whether it has been properly made. Special 
works furnish sufficient information concerning processes of 
manufacture, and it is essential to know here only the general 
composition of the grape- juice or "must" and how, by the 
natural process of fermentation, this may be altered in the 
finished product. 

The "must" contains sugars (mainly dextrose); dextrin; 
organic acids and salts, mainly tartaric and malic acids; salts of 
inorganic acids, chiefly phosphates, sulphates, and chlorides. 
Various extractive matters, which largely affect the color and flavor 
of the wine, together with a little tannin and albuminous sub- 
stances, are also present. The wine will contain, then, besides 
water, the following: Alcohol, glycerine, frequently some sugar 
that has escaped fermentation, ethers, which determine largely 
the "bouquet" of the wine, and more or less of the acids, salts, 
coloring and extractive matters of the must, together with vary- 
ing amounts of carbonic, acetic, and succinic acids. 

According to differences in their composition, wines may be 
divided into various classes, such as "dry" wines, which contain 
very little sugar, as distinguished from the sweet wines, in which 
a notable quantity of sugar has escaped fermentation, or to 
which an addition of sugar has been made subsequent to the 
main fermentation. Or they may be divided according to the 
content of alcohol into natural wines and those fortified by ad- 
dition of alcohol, as port, sherry, and madeira. 

The composition of the wine may be changed, moreover, by 
the various methods which are used for its "improvement," 



ANALYTICAL METHODS 191 

such as fortification already mentioned, plastering, petiotization, 
etc. Information regarding these methods will be found in 
some of the larger works mentioned in the bibliography. 

Determinations of value in judging the purity of wine are 
alcohol, glycerine, extract, ash, total and volatile acids. The 
actual percentages of these substances are not of so great value as 
certain relations between them, such as the ratio of ash to extract, 
extract to alcohol, alcohol to glycerine, alcohol to acids, and 
volatile to total acids. Examination for preservatives and for- 
eign coloring matters should also be made. It should, perhaps, be 
stated that the analytical procedure given here is to furnish 
practice in the examination of a fermented food product, and is 
by no means as thorough as might be needed to judge the quality 
or genuineness of a wine. 

Specific Gravity. — This is to be taken by means of the 
pyknometer at i5°.5 C. 

Notes. — Where the specific gravity of the sample is known, 
the various portions taken for analysis can be more conven- 
iently measured than weighed. The results can be calculated 
to per cent by weight by dividing the results expressed as grams 
per 100 c.c. by the specific gravity. 

Effervescing wines should, before analysis, be vigorously 
shaken in a large flask to hasten the escape of carbon dioxide. 
The liquid may then be poured from under the foam into an- 
other vessel. 

Alcohol. — Principle. — The alcohol is obtained freed from 
everything but water, and its amount determined by ascertain- 
ing the specific gravity of the mixture, and taking the per cent 
from the tables. 

Directions. — Measure (or weigh) 100 c.c. of the wine into a 
500-c.c. round-bottomed flask. Add 50 c.c. of water and if the 
wine is very acid a small pinch of precipitated calcium carbon- 
ate. With most wines this addition will not be necessary. 
Distill about 95 c.c. into a 100-c.c. graduated flask. Fill to the 
mark with distilled water, mix thoroughly, and take the specific 
gravity of the distillate at 15.5 C. with a pyknometer. The per- 



192 AIR, WATER, AND FOOD 

centage of absolute alcohol by volume corresponding to the 
observed density will be found in Table X, page 217. 

To find the alcohol by weight in the sample, multiply the per 
cent of alcohol by weight in the distillate as taken from the table, 
by the weight of the distillate and divide the result by the 
weight of the sample used. 

Notes. — The addition of calcium carbonate is to prevent the 
distillation of acetic acid. A certain amount of volatile ethers 
may also pass over into the distillate, but it is so slight that its 
influence may be neglected. 

Normal wines ordinarily contain between 4.5 and 12 per cent of 
alcohol except in the case of "fortified" wines, where the amount 
may be even 20 per cent. Fermentation does not yield more 
than about 14 per cent of alcohol. 

Extract. — The method to be employed depends on the pro- 
portion of extract. A preliminary calculation should be made 
by the aid of the formula 

x = 1 -j- d — d f , 
where x is the specific gravity of the dealcoholized wine, d the 
specific gravity of the wine, and d r the specific gravity of the 
distillate obtained in the determination of alcohol. The value 
for x is found from Table XI, page 220. 

Dry Wines. — (Having an extract content of less than 3 per 
cent.) Evaporate 50 c.c. on the water-bath to a sirupy con- 
sistency in a flat-bottomed platinum dish. Heat the residue in 
the oven at ioo° C. for two hours and a half, cool in a desiccator 
and weigh. 

Sweet Wines. — When the extract content is between 3 and 
6 per cent treat 25 c.c. of the sample as described under dry 
wines. When the amount of extract exceeds 6 per cent it is best 
to accept the result found from the table and not to determine 
it gravimetrically. 

Notes. — The gravimetric determination will be inaccurate 
with wines high in extract on account of the serious error caused 
by drying levulose at high temperatures. The figures in the 
table are based on determinations made at 75 C. in vacuo. 



ANALYTICAL METHODS 193 

Wine made from the juice of ripe grapes rarely contains less 
than 1.5 per cent of extract in the case of white wines and about 
2.0 per cent in the case of red wines. The amount of extract 
decreases of course with age. 

Alcohol-extract Ratio. — The municipal laboratory of Paris 
considers a wine " fortified" if the alcohol exceeds 4.5 times the 
extract for red wines and 6.5 for white wines. The extract and 
alcohol should both be expressed in per cent by weight. The 
amount of added alcohol is calculated by the municipal labora- 
tory by subtracting the " natural" alcohol (extract X 4.5 or 6.5) 
from the total alcohol. 

Ash. — Ignite the residue from the extract determination as 
described on page 180. 

Note. — The amount of ash in a natural wine averages about 
10 per cent of the extract, varying ordinarily between 0.14 per 
cent and 0.35 per cent. 

Glycerine. — The determination of glycerine, and the ratio 
of glycerine to alcohol is of much value in judging the purity of 
a wine. The determination of the glycerine, however, is rather 
difficult and requires some little experience in order to obtain 
good results. The official method of the Association of Agri- 
cultural Chemists will be found in Bur. of Chem., Bull. 107, 
(Rev. Ed.), p. 83. A more accurate modification, however, is 
that of Ross {Bull. 132, p. 85). 

Free Acids: Total Acidity Calculated as Tartaric Acid. — 

Measure 25 c.c. of the wine into a small beaker, heat just below 

N 
the boiling point to expel carbon dioxide, and titrate with — 

10 

sodium hydroxide and phenolphthalein. In the case of red 

wines use delicate red litmus paper, taking the end-point when 

a drop of the liquid placed upon the paper produces a blue spot 

in the middle of the portion moistened. Calculate the results as 

N 
tartaric acid. One c.c. — sodium hydroxide = 0.0075 gram of 

tartaric acid. 



194 AIR, WATER, AND FOOD 

Volatile Acids Calculated as Acetic Acid. — Measure 50 c.c. 

of wine into a 300-c.c. flask provided with a cork having two 

perforations. One is fitted with a tube 6 mm. in diameter and 

blown out to a bulb 40 mm. in diameter a short distance above 

the cork; this tube is connected with a condenser. The other 

perforation carries a tube reaching nearly to the bottom of the 

flask and drawn out to a small aperture at its lower end; this is 

connected with a 500-c.c. flask containing water. Heat both 

flasks to boiling; then lower the flame under that containing the 

wine, adjusting the flame so that the volume of liquid remains 

constant, and continue the distillation by means of steam until 200 

N 
c.c. have distilled. Titrate the distillate with — ■ sodium hydrox- 

10 

ide, using phenolphthalein as an indicator. Calculate the results 

N 
as acetic acid. One c.c. — sodium hydroxide = 0.0060 gram 

of acetic acid. 

Hortvet * has described a compact self-contained apparatus 
for determining the fixed and volatile acids in which the wine is 
surrounded by boiling water while the steam is being passed 
through, giving excellent results. 

Fixed Acids Calculated as Tartaric Acid. — These may be 
found by calculating the volatile acids as tartaric and sub- 
tracting the result from the total tartaric acid found by direct 
titration. 

Note. — The total acids in a wine vary usually between 0.45 
per cent and 1.5 per cent. The acid content is frequently 
diminished by aging or by the separation of cream of tartar. 
The volatile acid should, in general, not be over 0.12 to 0.16 
per cent, depending upon the age of the wine. A wine properly 
made should not have the volatile acid, estimated as acetic, ex- 
ceed one-fourth of the total free acid, calculated as tartaric. 

Coloring Matters: Detection of Coal-tar Dyes.j — Fifty c.c. 
of the sample are diluted to 100 c.c. with water, filtered if neces- 

* /. Ind. Eng. Chem., 1910, 31. 

f Sostegni and Carpentieri: Ztschr. anal. Chem., 35, 1896, 397. 



ANALYTICAL METHODS 195 

sary, faintly acidified with hydrochloric or acetic acid, and a 
piece of white woolen cloth, which has been thoroughly washed 
with hot water, is immersed in the solution and boiled for five to 
ten minutes. The cloth is then removed and thoroughly washed 
with boiling water, and boiled in a dilute solution of ammonia 
(1 : 50). With some of the dyes the color is stripped from the 
wool quite readily; with others it is necessary to boil for some 
time. The wool is removed, the ammoniacal solution made 
faintly acid with hydrochloric acid, and another piece of white 
wool is immersed and again boiled. This second dyeing fixes 
coal-tar dyes on the fibre, but fruit and vegetable colors remain 
on the first piece of wool. 

Notes. — It is absolutely necessary that the second dyeing 
should be made, as some of the coal-tar dyes will dye a dirty 
orange in the first acid bath which might be easily passed for 
vegetable color but on treatment in alkaline bath and second 
acid bath becomes a bright pink. 

Excess of acid should be avoided since some of the colors do 
not dye readily in strongly acid solution. 

Another advantage in the second dyeing is that if a large 
piece of woolen cloth is used in the first dyeing, and a small 
piece in the second dyeing, small amounts of coloring matter 
can be brought out much more decidedly in the second dyeing, 
where practically all of the vegetable coloring matter has been 
excluded. 

Several colors which are not coal-tar dyes, notably archil and 
archil derivatives, give reactions by this method and are liable 
to be confused with coal-tar colors. For hints as to the method 
for detecting these reference may be made to Bulletin 107, 
Bureau of Chemistry, page 190. 

The further separation and identification of the artificial 
colors is too difficult a matter to be taken up here. The student 
is referred for information on this point to the following: Mulli- 
ken: The Identification of Commercial Dyestuffs; Loomis: 
Circular 63, Bureau of Chemistry; Allen: Commercial Organic 



196 AIR, WATER, AND FOOD 

Analysis, 4th Ed., Vol. V; Green and others*: The Identi- 
fication of Dyestuffs on Animal Fibres. 

Preservatives. — The preservatives to be sought generally in 
wines are salicylic and benzoic acids and their salts. Sulphurous 
acid and sulphites are also used. For methods of detecting 
other substances less commonly employed, such as abrastol, beta- 
naphthol, etc., reference may be made to Bulletin 107 of the 
Bureau of Chemistry. Boric acid is occasionally used, but since 
a small amount of it is normally present in wines, tests, to be 
of value, should be quantitative. 

Salicylic Acid. — Acidify about 50 c.c. of the wine with 5 c.c. 
of dilute (1 -.3) sulphuric acid and extract in a separatory fun- 
nel with 25 c.c. of ether. Draw off the lower layer, wash the 
ether twice with water, using 10 c.c. each time and finally evapo- 
rate the ether in a porcelain dish at room temperature. To the 
residue in the dish add 2 to 3 drops of very dilute ferric chloride 
or better ferric alum solution (App. B). A deep purple or violet 
color indicates salicylic acid. 

Notes. — Not more than 50 c.c. should be used for the test, 
since a trace of salicylic acid seems normally present in some 
wines. 

The washing with water is to free the ether from traces of 
sulphuric acid which interferes with the development of the 
violet color. 

Care should be exercised in making the extraction with ether 
not to shake the separatory funnel too violently, since a trouble- 
some emulsion may result. 

Benzoic Acid.\ — Acidify about 100 c.c. of wine with sulphuric 
acid, extract with ether, and evaporate the ethereal solution as 
in the detection of salicylic acid. Treat the residue with 2 or 
3 c.c. of strong sulphuric acid. Heat till white fumes appear; 
organic matter is charred and benzoic acid is converted into 
sulpho-benzoic acid. A few crystals of ammonium nitrate are 
then added. This causes the formation of metadinitrobenzoic 

* /. Soc. Dyers and Colourists, 1905, 236. 
t Mohler: Bull. Soc. Chim. [3], 3, 1890, 414. 



ANALYTICAL .METHODS 197 

acid. When cool the acid is diluted with water and ammonia 
added in excess, followed by a drop or two of ammonium sulphide. 
The nitro-compound becomes converted into ammonium meta- 
diamidobenzoic acid, which possesses a red color. This reaction 
takes place immediately, and is seen at the surface of the liquid 
without stirring. 

Sulphurous Acid and Sulphites. — See directions under Beer, 
page 198. 

BEER AND OTHER MALT LIQUORS 

Before analysis the sample must be thoroughly shaken in a 
large flask, in order to remove carbon dioxide. 

Specific Gravity. — Taken with a pyknometer at 15.5 C. 

Alcohol. — Determined as in the analysis of wine. The ad- 
dition of calcium carbonate will not be necessary. If the sample 
foams much this can be prevented by the addition of about half 
a gram of tannin before distilling. 

Extract. — Determine the extract content corresponding to 
the specific gravity of the dealcoholized beer according to Table 
XIII. For this purpose employ the formula 

Sp = g + (i- g'), 

in which Sp is the specific gravity of the dealcoholized beer, g 
the specific gravity of the beer, and g' the specific gravity of the 
distillate obtained in the determination of alcohol. Instead of 
using this formula the residue from the distillation of alcohol is 
sometimes diluted to the original volume, and its specific gravity 
taken. This is often impracticable owing to the necessity of 
employing tannic acid to prevent foaming in the distilling flask, 
and owing to the coagulation of proteids during the distillation. 

Note. — The extract of beer cannot be accurately determined 
by evaporation and drying at the boiling-point of water because 
of the dehydration of the maltose. 

Ash. — Evaporate 25 c.c. to dryness and determine as de- 
scribed on page 180. 

Free Acids. — Heat 20 c.c. to incipient boiling to expel carbon 
dioxide and titrate as in the analysis of wine. Fixed acids, con- 



198 AIR, WATER, AND FOOD 

sisting principally of lactic and succinic, are calculated as lactic 

N 
acid. One c.c. of — sodium hydroxide = 0.0090 gram of lactic 
10 

acid. 

Reducing Sugar. — Dilute 25 c.c. of the beer, freed from car- 
bon dioxide, to 100 c.c. Determine the reducing sugar in 25 c.c. 
of this solution as directed on page 145, enough water being 
added to make the total volume of the Fehling's solution-sugar 
mixture 100 c.c. Express the results in terms of maltose, as 
given in Table XII. 

Preservatives. — The preservatives most commonly employed 
in beer are benzoic and salicylic acids and their sodium salts, 
sulphites and fluorides. 

Benzoic and Salicylic Acids. — Detected as described under 
Wine. 

Sulphites. — Qualitative Test. — Use an apparatus similar to 
that described for the determination of volatile acids in wine. 
To 50 c.c. of the sample add about a gram of sodium bicarbonate, 
20 c.c. of 20 per cent phosphoric acid, and immediately con- 
nect the flask with the condenser. Pass steam through the 
flask until about 20 c.c. have collected in the distillate. To the 
distillate add bromine water in slight excess and boil. Expel 
the excess of bromine and test for sulphuric acid with hydro- 
chloric acid and barium chloride in the usual manner. 

Notes. — The method described does not distinguish between 
free sulphurous acid and that present in the form of sulphites. 
The former can be distilled without the addition of phosphoric 
acid. 

The presence of sulphites in a sample should not be con- 
sidered evidence of added preservatives unless an excessive 
amount is found, since the use of sulphured malt or hops may 
introduce a small amount. To obtain conclusive data, a quan- 
titative determination of the amount present should be made. 

This can be done by a method similar to that used for its 
detection, distilling in a current of carbon dioxide, absorbing 
the sulphur dioxide in bromine water and determining the re- 



ANALYTICAL METHODS 1 99 

suiting sulphuric acid as barium sulphate. In the case of food 
products, where sulphides are liable to be present also, the steam 
should pass through a solution of copper sulphate* before en- 
tering the condenser in order to remove any hydrogen sulphide 
formed by the action of the phosphoric acid. Details of the 
method will be found in Leach's Food Analysis. 

In Bulletin 107 it is recommended to distill into a standard 
iodine solution and titrate the excess of iodine. This has the 
disadvantage, however, that other iodine-reducing substances 
than sulphurous acid may pass into the distillate and give too 
high results. 

Fluorides. — The well-known qualitative test for fluorides by 
etching a glass plate may be modified by the use of a suitable 
condenser and made sufficiently delicate to be used here. It is 
possible also by suitable regulation of the temperature to make 
the test approximately quantitative.! 

Flavoring Extracts 

The work on alcoholic liquids can be pleasantly varied by 
substituting for it, in some cases, the determination of alcohol 
and other important components of the usual flavoring essences, 
the most important of which are vanilla and lemon. Several 
important types of analytical methods, such as the determina- 
tion of essential oils and quantitative extraction with volatile 
solvents, are also brought to the attention of the student. 

VANILLA 

Vanilla extract is a dilute alcoholic tincture of the vanilla 
bean, the fruit of a climbing plant of the orchid family. The 
best grades are made by allowing the cut and bruised beans to 
macerate in the alcohol for several months, the liquid thus 
obtained being deep brown in color, with a delightful perfume 
and flavor. Sugar is added to assist in the extraction and to 
sweeten the product. 

* Winton and Bailey: J. Am. Chem. Soc, 1907, 1499. 

t Woodman and Talbot: J. Am. Chem. Soc, 1906, 1437; 1907, 1362. 



200 



AIR, WATER, AND FOOD 



The cost of a quart of the pure extract, according to Winton,* 
is from about 60 cents to $2.50, depending chiefly upon the 
grade of beans used. 

The composition of five pure vanilla extracts, made from 
beans of different grades, is given in the following table,| the 
results being expressed in per cent by weight: 



Grade of bean. 


Specific 
gravity. 


Vanillin. 


Alcohol. 


Total 
residue. 


Cane- 
sugar. 


Mexican (whole) 

Mexican (cut) 

South American (whole) . 

Bourbon (whole) 

Tahiti (whole) 


I. 0159 
I .0146 
I . 1009 
I .0166 
I. 0104 


O.125 
O.065 
0.215 
O.138 
0.108 


37-96 
39-92 
38.58 
38.32 
38.84 


22.6o 
23.10 
22.00 
23.13 

21-75 


19.90 
19.20 
19.OO 
20.40 
20.00 



The adulteration of vanilla extract consists principally in the 
use of extract of Tonka bean, a cheap substitute somewhat re- 
sembling vanilla in its flavor, in the use of artificial prepara- 
tions of the active principles of vanilla and tonka, vanillin and 
coumarin, and in the addition of artificial color, usually cara- 
mel. A cheap extract may be entirely an artificial mixture, 
made of artificial vanillin or coumarin, or both, in weak alcohol, 
colored with caramel. An occasional adulteration is the use of 
alkali, such as potassium bicarbonate, to hold the resin in solu- 
tion and permit the use of a more dilute alcohol. 

An extract of vanilla of good quality should contain from 25 
to 40 per cent of alcohol, from 0.10 to 0.20 per cent of vanillin, 
and give a good precipitate of vanilla resins. Imitation extracts 
usually show one or several of the following characteristics: 
Presence of coumarin; deficiency in resins; abnormally low or 
high content of vanillin; presence of artificial color; low lead 
number. 

Analytical Methods. — Alcohol. — Measure 25 c.c. of the 
sample, add 100 c.c. of water, and determine the alcohol by 

* Conn. Agr. Exp. Sta. Report, 1901, 150. 
t Conn. Agr. Exp. Sta. Report, 1901, 150. 



ANALYTICAL METHODS 201 

volume, as directed on page 191, omitting the use of calcium 
carbonate and tannic acid. 

Vanillin and Coumarin. — (Modified method of Hess and 
Prescott).* Weigh 50 grams into a 250-c.c. beaker with marks 
showing volumes of 80 c.c. and 50 c.c., dilute to 80 c.c., and 
evaporate to 50 c.c. in a water-bath kept at 70 C. Dilute again 
to 80 c.c. and evaporate to 50 c.c. Transfer to a 100-c.c. flask, 
rinsing out the beaker with hot water, add 25 c.c. of lead acetate 
solution (80 grams of neutral lead acetate made up to a liter), 
make up to the mark with water, shake and allow it to stand 
over night. Decant on a small dry filter, pipette off 50 c.c. of 
the nitrate, and extract it four times in a separatory funnel, 
using 15 c.c. of ether each time. 

Combine the ether extracts in another separatory funnel and 
wash five times with 2 per cent ammonium hydroxide, using 
10 c.c. the first time and 5 c.c. for each subsequent shaking. Set 
aside the combined ammoniacal solutions for the determination 
of vanillin. 

Transfer the ether solution to a weighed dish and allow the 
ether to evaporate at room temperature. Dry in a desiccator 
over sulphuric acid and weigh. If the residue is not white and 
crystalline stir it for fifteen minutes with 15 c.c. of petroleum 
ether (boiling point 30 to 40 C.) and decant the clear liquid into 
a beaker. Repeat the treatment with petroleum ether two or 
three times. Allow the residue to stand in the air until ap- 
parently dry, completing the drying in the desiccator. Weigh, 
and deduct the weight from the weight of the residue obtained 
after the ether evaporation, thus obtaining the weight of the 
coumarin. This may be recognized by its characteristic odor, 
resembling that of " sweet grass," and by Leach's testf as 
follows: Dissolve the residue in a few drops of hot water, 

N 
and add one or two drops of — iodine in potassium iodide. 

On stirring with a rod, a brown precipitate will form, which 

* /. Am. Chem. Soc, 1905, 719; Bur. of C hem., Bull. 137, 68. 
f Leach: "Food Inspection and Analysis," 3d Ed., p. 867. 



202 AIR, WATER, AND FOOD 

will gather into dark green flocks. The reaction is especially 
marked if carried out in a white porcelain crucible or dish. 

Slightly acidulate the ammoniacal solution reserved for vanillin 
with 10 per cent hydrochloric acid. Cool, and shake out in a 
separatory funnel with four portions of ether, as described for 
the first ether extraction. Evaporate the ether at room tem- 
perature in a weighed dish, dry over sulphuric acid, and weigh 
the vanillin. 

If the residue is white, it may be safely assumed, in the majority 
of cases, that it is pure vanillin. If dark colored, however, the 
dry residue should be extracted not less than fifteen times with 
boiling petroleum ether (boiling point 40 C. or below). Evapo- 
rate the solvent, dry and weigh the vanillin. A small amount 
of the residue, dissolved in two drops of concentrated hydro- 
chloric acid, should give a pink color upon the addition of a 
crystal of resorcin. 

Notes. — The separation of vanillin and coumarin is based 
on the differences in their chemical constitution. Vanillin is 
hydroxymethoxybenzoic aldehyde, while coumarin is the anhy- 
dride of orthohydroxycinnamic acid. On account of the alde- 
hydic nature of the vanillin, the separation by dilute ammonia 
is possible, the aldehyde ammonia compound of vanillin being 
readily soluble in water, while the coumarin remains wholly in 
the ether. 

If a portion of the vanillin, after weighing, be dissolved in two 
or three drops of ether and allowed to evaporate spontaneously 
on a microscope slide it shows a characteristic appearance with 
polarized light. The vanillin crystallizes in slender needles, 
forming star-shaped clusters. These give a brilliant play of 
colors with crossed Nicols, even without the selenite plate. 

Normal Lead Number. — To a 10-c.c. portion of the filtrate 
obtained from the lead acetate in the determination of vanillin 
and coumarin add 25 c.c. of water, sulphuric acid in slight excess, 
and 100 c.c. of 95 per cent alcohol, let stand over night, filter on a 
Gooch crucible, wash with alcohol, dry in the oven of the water- 
bath, ignite for three minutes at low redness, taking care to 



ANALYTICAL METHODS 203 

avoid the reducing flame, and weigh the lead sulphate. Cal- 
culate the normal lead number by the following formula 

_ 100 X 0.6831 (S - W) 
5 

in which P = normal lead number, S = grams of lead sulphate 
corresponding to 2.5 c.c. of the lead acetate solution, as deter- 
mined from a blank analysis, and W = grams of lead sulphate 
obtained in 10 c.c. of the filtrate, as just described. 

Note. — The normal lead number of genuine vanilla extracts 
determined by this method ranges from 0.35 to 0.60. Artificial 
extracts generally are distinctly lower, sometimes as low as 0.03. 

More accurate results can be obtained by regulating more 
closely the time and temperature during the standing of the so- 
lution with lead acetate. Winton and Berry* recommend stand- 
ing 18 hours at 37 to 40 C. They find that, determined in this 
manner, the minimum normal lead number for vanilla extracts 
prepared according to the U. S. Pharmacopoeia is 0.40. 

Resins. — Evaporate 25 or 50 c.c. of the extract to one-third 
its volume on the water-bath in order to remove the alcohoL 
Make up to the original volume with hot water. If no alkali 
has been used in the manufacture of the extract, the resin 
should appear at this point as a flocculent brown residue. Add 
acetic acid in slight excess, allow the evaporating-dish to stand 
in a warm place for a time to separate the resin completely, 
and filter. Wash the residue on the filter, and save both the 
filtrate and residue. Test the resin by placing pieces of the 
filter, with the resin attached, in a few cubic centimeters of 
dilute caustic potash. The resin is dissolved with a deep red 
color, and on acidifying is again precipitated. Test the filtrate 
by adding to it a few drops of basic lead acetate. A bulky pre- 
cipitate is formed, on account of the organic acid, gums, etc., 
present. 

Confirm the resin test by shaking 5 c.c. portions of the ex- 
tract in separate test-tubes with 10 c.c. of amyl alcohol and 

* Bur. of Chem., Bull. 137, 120. 



204 AIR, WATER, AND FOOD 

10 c.c. of ether. With pure extracts the upper layers will be 
colored, varying from light yellow to deep brown; with artificial 
extracts, free from resin, the amyl alcohol and ether layers will 
be uncolored. 

Note. — While the artificial vanillin, as sold on the market 
and used in the manufacture of low-grade extracts, is identical 
with the vanillin of the vanilla bean, it is true that pure extracts 
owe their value and flavor to other ingredients as well as to the 
vanillin present. Among these " extractive matters" the resins 
are important from an analytical standpoint, serving by their 
presence or absence to determine whether true vanilla is present 
or the extract entirely artificial. As a quick and ready test, 
serving to distinguish artificial extracts from genuine prepara- 
tions of the vanilla bean, the amyl alcohol and ether tests will 
be found especially useful. 

Color : Caramel. — Caramel is the color commonly used in 
vanilla extracts, although coal-tar dyes have been found. The 
presence of dyes is sometimes indicated by the color of the 
amyl alcohol in testing for the resin, they being in many cases 
soluble in amyl alcohol, but insoluble in ether. 

Lead Acetate Test. — The coloring matter present in vanilla 
extracts is almost completely removed when the dealcoholized 
extract is treated with a few cubic centimeters of basic lead 
acetate solution. When caramel is present, the filtrate and 
precipitate, if any, have the characteristic red-brown color of 
caramel. 

Marsh Test* — Evaporate 25 c.c. of the extract until the odor 
of alcohol is no longer apparent and the liquid is reduced to a 
thick sirup. Dissolve the residue in water and alcohol, using 
26.3 c.c. of 95 per cent alcohol, and making up to volume in a 
50-c.c. flask with water. Transfer 25 c.c. of this solution to a 
separatory funnel; add 25 c.c. of the Marsh reagent and shake, 
not too vigorously, to avoid emulsification. Allow the layers 
to separate and repeat the shaking twice more. After the 
layers have separated clearly, run off the lower layer into a 25-c.c. 

* Bur. of C hem., Bull. 152, p. 149. 



ANALYTICAL METHODS 205 

cylinder, and make up to volume with 50 per cent (by volume) 
alcohol. Filter if necessary and compare in a colorimeter with 
the remaining 25-c.c. portion (which has not been extracted with 
the reagent) and express the results as per cent of color insolu- 
ble in amyl alcohol. 

The Marsh reagent is prepared as follows: Mix 100 c.c. of 
amyl alcohol, 3 c.c. of sirupy phosphoric acid, and 3 c.c. of water; 
shake before using. If the reagent becomes colored on standing, 
the amyl alcohol should be redistilled over 5 per cent phosphoric 
acid. 

Note. — The method is based on the greater solubility in acid 
amyl alcohol of the natural color of the vanilla bean as com- 
pared with caramel. A genuine extract, uncolored with caramel, 
will not usually show more than 40 per cent of color insoluble in 
amyl alcohol. 

LEMON 

Lemon extract is usually made by dissolving oil of lemon, 
obtained by expression or distillation from the rind of the lemon, 
in strong alcohol. The product is sometimes colored with the 
color of lemon peel. The Federal standards * require a content 
of lemon oil of at least 5 per cent by volume. The expensive 
ingredient of the extract is the alcohol, since alcohol of at least 
80 per cent strength by volume must be used to dissolve 5 per 
cent of lemon oil; hence in making cheap extracts the manu- 
facturer endeavors to use a dilute alcohol, even under the neces- 
sity of omitting a portion or all of the oil of lemon. 

The common forms of adulteration of lemon extract are the 
use of weak alcohol and consequent deficiency of lemon oil, as 
already noted ; the substitution for the lemon oil of small amounts 
of stronger oils, as oil of citronella, oil of lemon-grass, and the 
like; the use of citral, the odorous principle of lemon oil, used 
for making the so-called "terpeneless lemon extracts;" and the 
coloring of the extracts by coal-tar colors or turmeric. 

Preliminary Test. — To a little of the extract in a test-tube 
add seven or eight times its volume of water. A high-grade ex- 

* U. S. Dept. Agric, Office of the Secretary, Circ. 19. 



206 AIR, WATER, AND FOOD 

tract will show a heavy cloud, due to the precipitation of the 
lemon oil. If no cloudiness or turbidity appears it may be safely 
inferred that no oil is present. 

Alcohol. — The determination of alcohol is somewhat com- 
plicated in this case by the presence of the volatile oil of lemon 
which must be removed before distilling. 

Dilute 20 c.c. of the extract to 100 c.c. with water, and pour 
the mixture into a dry Erlenmeyer flask containing 5 grams of 
light magnesium carbonate. Shake thoroughly and filter 
through a dry filter. Measure 50 c.c. of the clear filtrate, add 
about 15 c.c. of water, and distill 50 c.c, as directed on page 191. 
From the specific gravity of the distillate determine the per cent 
of alcohol by volume, and this, multiplied by 5, will give the 
percentage in the original extract. 

Note. — The magnesia serves to absorb the precipitated oil 
and prevent it from passing through the filter. 

Lemon Oil. — Pipette 20 c.c. of the extract into a Babcock 
milk bottle; add 1 c.c. dilute hydrochloric acid (1 : 1); then 
add from 25 to 28 c.c. of water previously warmed to 6o°C; 
mix and let stand in water at 6o° for five minutes; whirl in 
centrifuge for five minutes; fill with warm water to bring the 
oil into the graduated neck of the flask; repeat whirling for 
two minutes; stand the flask in water at 6o° C. for a few min- 
utes and read the per cent of oil by volume. If the determina- 
tion is not made in duplicate the flask should be balanced by 
another containing an equal weight of water. In case oil of 
lemon is present in amounts over 2 per cent add to the percent- 
age of oil found 0.4 per cent to correct for the oil retained in 
solution. If less than 2 per cent and more than 1 per cent is 
present, add 0.3 per cent for correction. 

Color. — Test for coal-tar colors by evaporating a portion of 
the extract to dryness on the water-bath. Dissolve the residue 
in water and carry out the double dyeing method, as described 
on page 194. 

It may be advisable not to add any acid to the dye bath, as 
Naphthol Yellow S, which is commonly used in lemon extracts, 
dyes wool best from a nearly neutral bath. 



ANALYTICAL METHODS 207 

To test for turmeric add to a portion of the sample three 
drops of saturated boric acid solution, one small drop of dilute 
(1 : 10) hydrochloric acid, and a piece of filter-paper so ar- 
ranged that it is only half immersed in the liquid. Evaporate 
to dryness on the water-bath. In the presence of turmeric the 
paper will be colored pink and the test may be confirmed as 
described on page 154. Excess of hydrochloric acid should be 
avoided as in testing for boric acid. 

To show the presence of natural color derived from lemon 
peel the following reactions will be found helpful : * Dilute a few 
cubic centimeters of the extract until the color has nearly dis- 
appeared and divide the solution between two test-tubes. To 
one add a few drops of concentrated hydrochloric acid and to 
the other a few drops of strong ammonia. In the presence of 
natural color a distinct yellow color should result in each case. 

Citral. — See Bur. of Chem., Bull. 137, 70. 

* Albrech: Bur. of Chem., Bull. 137, 71. 



APPENDICES 



APPENDIX A 

TABLE I 

TENSION OF AQUEOUS VAPOR IN MILLIMETERS OF MERCURY FROM O TO 3O.9 C, 
REDUCED TOO° AND SEA-LEVEL 





0.0 


O.I 


0.2 


0.3 


0.4 


o.S 


0.6 


0.7 


0.8 


0.9 


o° 


4-57 


4.60 


4.64 


4.67 


4.70 


4-74 


4-77 


4.80 


4.84 


4.87 


I 


4.91 


4-94 


4.98 


5.02 


5-05 


5 09 


5-12 


5-i6 


5.20 


523 


2 


5-27 


5-31 


5-35 


5-39 


5-42 


5 -46 


5-5o 


5-54 


5-58 


5.62 


3 


5-66 


5-7o 


5-74 


5-78 


5.82 


5-86 


5 90 


5-94 


5-99 


6.03 


4 


6.07 


6. 11 


6.15 


6.20 


6.24 


6.28 


6-33 


6.37 


6.42 


6.46 


5 


6.51 


6-55 


6.60 


6.64 


6.69 


6.74 


6.78 


6.83 


6.88 


6.92 


6 


6.97 


7.02 


7.07 


7.12 


7.17 


7.22 


7.26 


7-31 


7-36 


7.42 


7 


7-47 


7-52 


7-57 


7.62 


7.67 


7.72 


7.78 


7-8 3 


7.88 


7-94 


8 


7-99 


8.05 


8.10 


8.15 


8.21 


8.27 


8.32 


8.38 


8-43 


8-49 


9 


8-55 


8.61 


8.66 


8.72 


8.78 


8.84 


8.90 


8.96 


9.02 


9.08 


10 


9.14 


9.20 


9.26 


9-32 


9-39 


9-45 


9-51 


9-58 


9.64 


9.70 


11 


9-77 


9-83 


9.90 


9.96 


10.03 


10.09 


10.16 


10.23 


10.30 


10.36 


12 


10.43 


10.50 


10.57 


10.64 


10.71 


10.78 


10.85 


10.92 


10.99 


11.06 


13 


11 .14 


11 .21 


11.28 


11.36 


H-43 


11.50 


11.58 


11.66 


n-73 


11. 81 


14 


11.88 


11 .96 


12.04 


12.12 


12.19 


12.27 


12.35 


12.43 


12.51 


12.59 


15 


12.67 


12.76 


12.84 


12.92 


13.00 


13.09 


I3-I7 


13-25 


13-34 


13-42 


16 


i3-5i 


13.60 


13-68 


13-77 


13-86 


13-95 


14.04 


14.12 


14.21 


14-30 


17 


14.40 


14.49 


14.58 


14.67 


14.76 


14.86 


14-95 


15.04 


15-14 


15-23 


18 


15-33 


15-43 


15-52 


15.62 


15-72 


15.82 


15-92 


16.02 


16.12 


16.22 


19 


16.32 


16.42 


16.52 


16.63 


16.73 


16.83 


16.94 


17.04 


17-15 


17.26 


20 


17.36 


17-47 


17-58 


17.69 


17.80 


17.91 


18.02 


18.13 


18.24 


i8.35 


21 


18.47 


18.58 


18.69 


18.81 


18.92 


19.04 


19.16 


19.27 


19-39 


19-51 


22 


19.63 


19-75 


19.87 


19.99 


20.11 


20.24 


20.36 


20.48 


20.61 


20.73 


23 


20.86 


20.98 


21 . 11 


21.24 


21.37 


21.50 


21.63 


21.76 


21.89 


22.02 


24 


22.15 


22.29 


22.42 


22.55 


22.69 


22.83 


22.96 


23.10 


23.24 


23.38 


25 


23-52 


23.66 


23.80 


23-94 


24.08 


24.23 


24-37 


24.52 


24.66 


24.81 


26 


24.96 


25.10 


25-25 


25.40 


25-55 


25.70 


25.86 


26.01 


26. 16 


26.32 


27 


26.47 


26.63 


26.78 


26.94 


27.10 


27.26 


27.42 


27.58 


27.74 


27.90 


28 


28.07 


28.23 


28.39 


28.56 


28.73 


28.89 


29.06 


29.23 


29.40 


29-57 


29 


29.74 


29.92 


30.09 


30.26 


30-44 


30.62 


30.79 


30.97 


3I-I5 


31-33 


30 


3i-5i 


31.69 


3187 


32.06 


32.24 


32.43 


32.61 


32.80 


3299 


33.18 



208 



APPENDIX A 



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M 



APPENDIX A 



211 





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212 



AIR, WATER, AND FOOD 






06 

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APPENDIX A 



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APPENDIX A 



215 



TABLE VII 

SULPHATES IN WATER 

(Reduced from table in article by H. F. Muer, J. Ind. Eng. Chem., 1911, 

Vol. 3, p. 553) 



Depth, 


S0 3 , pts. per 


Depth, 


S0 3 , pts. per 


Depth, 


SO3, pts. per 


Depth, 


S0 3 , pts. per 


cm. 


million. 


cm. 


million. 


cm. 


million. 


cm. 


million. 


i-5 


3I30 


6.7 


72.O 


II. 9 


47-3 


17,1 


37-3 


1 


6 


280.0 


6 


8 


71 


3 


I2.0 


47 


.0 


17.2 


37 


3 


1 


7 


250.O 


6 


9 


70 


5 


12. 1 


46 


.8 


17-3 


37 





1 


8 


238.0 


7 


.0 


69 


8 


12.2 


46 


•5 


17-4 


36 


8 


1 


9 


225.O 


7 


.1 


69 





12.3 


46 


■3 


17-5 


36 


8 


* 





213.O 


7 


.2 


68 


3 


12.4 


46 


.0 


17.6 


36 


5 


2 


1 


200.0 


7 


•3 


67 


5 


12.5 


45 


.8 


17.7 


36 


3 


2 


2 


190.O 


7 


•4 


66 


8 


12.6 


45 


•5 


17.8 


36 





2 


3 


183.O 


7 


5 


66 





12.7 


45 


3 


17.9 


36 





2 


4 


I7S-0 


7 


6 


65 


3 


12.8 


45 





18.0 


35 


8 


2 


5 


168.O 


7 


•7 


64 


8 


12.9 


44 


.8 


18. 1 


35 


8 


* 


6 


163.0 


7 


8 


64 





13.0 


44 


5 


18.2 


35 


5 


2 


7 


158.0 


7 


9 


63 


5 


13- 1 


44 


3 


18.3 


35 


3 


2 


8 


I530 


8 





62 


8 


13.2 


44 





18.4 


35 


3 


2 


9 


148.O 


8 


1 


62 


3 


13-3 


43 


8 


18.5 


35 





3 





I43.0 


8 


2 


61 


8 


13-4 


43 


5 


18.6 


35 





3 


1 


138.O 


8 


3 


61 





13-5 


43 


3 


18.7 


34 


8 


3 


2 


I35-0 


8 


4 


60 


5 


136 


43 


3 


18.8 


34 


5 


3 


3 


130.0 


8 


5 


60 





13 -7 


43 





18.9 


34 


5 


3 


4 


128.O 


8 


6 


59 


5 


13-8 


42 


8 


19.0 


34 


3 


3 


5 


125.O 


8 


7 


59 





13-9 


42 


5 


19. 1 


34 


3 


3 


6 


122.5 


8 


8 


58 


5 


14.0 


42 


5 


19.2 


34 





3 


7 


120.0 


8 


9 


58 





14. 1 


42 


3 


19-3 


33 


8 


3 


8 


«7-5 


9 





57 


5 


14.2 


42 





19.4 


33 


8 


3 


9 


115. 


9 


1 


57 





14-3 


4i 


8 


19-5 


33 


5 


4 





112. 5 


9 


2 


56 


5 


14.4 


4i 


5 


19.6 


33 


5 


4 


1 


110.0 


9 


3 


56 


3 


14-5 


4i 


5 


19.7 


33 


3 


4 


2 


107.5 


9 


4 


55 


8 


14.6 


4i 


3 


19.8 


33 





4 


3 


105.0 


9 


5 


55 


3 


14-7 


4i 





19.9 


33 





4 


4 


102.5 


9 


6 


54 


8 


14.8 


40 


8 


20.0 


32 


8 


4 


5 


100. 


9 


7 


54 


5 


14.9 


40 


5 


20.1 


32 


5 


4 


6 


98-3 


9 


8 


54 





150 


40 


5 


20.2 


32 


5 


4 


7 


96-5 


9 


9 


53 


8 


151 


40 


3 


20.3 


32 


3 


4 


8 


94.8 


10 





53 


3 


152 


40 





20.4 


32 





4 


9 


93 


10 


1 


52 


8 


15-3 


40 





20.5 


32 





5 





91-5 


10 


2 


52 


5 


15-4 


39 


8 


20.6 


3i 


8 


5 


1 


90.0 


10 


3 


52 


3 


15-5 


39 


8 


20.7 


31 


5 


5 


2 


88.5 


10 


4 


5i 


8 


15-6 


39 


5 


20.8 


3i 


5 


5 


3 


87-3 


10 


5 


5i 


5 


15-7 


39 


3 


20.9 


3i 


3 


5 


4 


85.8 


10 


6 


5i 





15-8 


39 


3 


21 .0 


31 


3 


5 


5 


84-5 


10 


7 


50 


8 


15-9 


39 





21 .1 


3i 





5 


6 


83-3 


10 


8 


50 


5 


16.0 


39 





21 .2 


30 


8 


5 


7 


82.0 


10 


9 


50 


3 


16. 1 


38 


8 


21.3 


30 


8 


5 


8 


81.0 


11 





50 





16.2 


38 


5 


21.4 


30 


5 


5 


9 


80.0 


11 


1 


49 


5 


16.3 


38 


5 


21.5 


30 


3 


6 





78.8 


11 


2 


49 


3 


16.4 


38 


3 


21 .6 


30 


3 


6 


1 


77.8 


11 


3 


48 


8 


16.5 


38 


3 


21.7 


30 





6 


2 


76.8 


11 


4 


48 


5 


16.6 


38 





21.8 


30 





6 


3 


75-8 


11 


5 


48 


3 


16.7 


38 





21 .9 


29 


8 


6 


4 


74.8 


11 


6 


48 





iS-8 


37 


8 


22.0 


29 


5 


6 


5 


73-8 


11 


7 


47 


8 


16.9 


37 


5 








6 


6 


73 -o 


11 


8 


47 


5 


17.0 


37 


5 









2l6 



AIR, WATER, AND FOOD 



TABLE VIII 

TABLE OF HARDNESS, SHOWING THE PARTS OF CALCIUM CARBONATE (CaCC*) IN 

1,000,000 FOR EACH TENTH OF A CUBIC CENTIMETER 

OF SOAP SOLUTION USED 





0.0 


O.I 


0.2 


0.3 


0.4 


0.5 


0.6 


0.7 


0.8 


0.9 




cu. cm. 


cu. cm. 


cu. cm. 


cu. cm. 


cu. cm. 


cu. cm. 


cu. cm. 


cu. cm. 


cu. cm. 


cu. cm. 


0.0 
















O.O 


1.6 


3-2 


1.0 


4.8 


6 


3 


7-9 


9 


5 


II .1 


12.7 


14-3 


15-6 


16.9 


18.2 


2.0 


19 -5 


20 


8 


22. 1 


23 


4 


24.7 


26.O 


27-3 


28.6 


29.9 


31.2 


3-o 


32.5 


33 


8 


35-1 


36 


4 


37-7 


39-0 


40.3 


41.6 


42.9 


44-3 


4.0 


45-7 


47 


1 


48.6 


50 





5i-4 


52-9 


54-3 


55-7 


57-i 


58.6 


5-o 


60.0 


61 


4 


62.9 


64 


3 


65-7 


67.1 


68.6 


70.0 


7i-4 


72-9 


6.0 


74-3 


75 


7 


77.1 


78 


6 


80.0 


81.4 


82.9 


84.3 


85-7 


87.1 


7.0 


88.6 


90 





91.4 


92 


9 


94-3 


95-7 


97.1 


98.6 


100. 


101.5 


8.0 


103.0 


104 


5 


106.0 


107 


5 


109.0 


no. 5 


112. 


II3-5 


115. 


116. 5 


9.0 


118. 


119 


5 


121. 1 


122 


6 


124. 1 


125.6 


127. 1 


128.6 


130. 1 


131. 6 


10. 


133- 1 


134 


6 


136. 1 


137 





139- 1 


140.6 


142. 1 


143-7 


145-2 


146.8 


11. 


148.4 


150 





151. 6 


153 


2 


154.8 


156.3 


157-9 


159-5 


161. 1 


162.7 


12.0 


164-3 


165 


9 


167.5 


169 





170.6 


172.2 


173-8 


175-4 


177.0 


178.6 


13.0 


180.2 


181 


7 


183 -3 


184 


Q 


186.5 


188. 1 


189.7 


I9I-3 


192.9 


194.4 


14.0 


196.0 


197 


6 


199.2 


200 


8 


202.4 


204.0 


205.6 


207.1 


208.7 


210.3 


150 


211 .9 


213 


5 


215. 1 


2l6 


8 


218.5 


220.2 


221.8 


223-5 


225.2 


226.9 



TABLE IX 

FOR CORRECTING THE SPECIFIC GRAVITY OF MILK ACCORDING TO TEMPERATURE 
ADAPTED FROM THE TABLE OF VIETH 

(Temperature in Degrees Centigrade) 



Specific 
gravity. 


10° 


ii° 


12° 


13° 


14° 


i5° 


16 


17° 


18 


19° 


20° 


I.025 


24.1 


24-3 


24-5 


24.6 


24.7 


24.9 


25- 1 


25-3 


25-4 


25.6 


25 9 


26 


25.1 


25.2 


25 


4 


25 


5 


25-7 


25 


Q 


26. 1 


26 


3 


26 


5 


26 


7 


27.0 


27 


26.1 


26.2 


26 


4 


26 


5 


26.7 


26 


9 


27.1 


27 


4 


27 


5 


27 


7 


28.0 


28 


27.0 


27.2 


27 


4 


27 


5 


27.7 


27 





28.1 


28 


4 


28 


5 


28 


7 


29.0 


29 


28.0 


28.2 


28 


4 


28 


5 


28.7 


28 


9 


29.1 


29 


4 


29 


5 


29 


8 


30.1 


3° 


29.0 


29. 1 


29 


3 


29 


5 


29.7 


29 


9 


30.1 


30 


4 


30 


5 


3° 


8 


3ii 


31 


29.9 


30.1 


30 


3 


30 


4 


30.6 


30 


Q 


31.2 


31 


4 


31 


5 


31 


8 


32.2 


32 


30-9 


3ii 


3i 


3 


31 


4 


3i-6 


3i 


9 


32.2 


32 


4 


32 


6 


32 


9 


33-2 


33 


31.8 


32.0 


32 


3 


32 


4 


32.6 


32 


9 


33-2 


33 


4 


33 


6 


33 


9 


34-2 


34 


32.7 


33-0 


33 


2 


33 


4 


33-6 


33 


9 


34-2 


34 


4 


34 


6 


34 


9 


35-2 


35 


33-6 


33-9 


34-i 


34-4 


34-6 


34-9 


35-2 


35 


4 


35-6 


35 





36.2 



Directions. — Find the observed gravity in the left-hand column. Then, in 
the same line, and under the observed temperature, will be found the corrected 
reading. 



APPENDIX A 



217 



TABLE X 

PERCENTAGE OF ALCOHOL FROM THE SPECIFIC GRAVITY AT 

15 °. 5 c. (hehner) 





Per cent 


Per cent 




Per cent 


Per cent 




Per cent 


Per cent 


Sp.gr. 


alcohol 


alcohol 


Sp. gr. 


alcohol 


alcohol 


Sp. gr. 


alcohol 


alcohol 


I5°o C. 


by 


by 


I5°.5 C. 


by 


by 


I5°.S C. 


by 


by 




weight. 


volume. 




weight. 


volume. 




weight. 


volume. 


I . OOOO 


0.00 


0.00 














0.9999 


0.05 


0.07 


0-9959 


2 33 


2 93 


O.9919 


4.69 


5 86 


8 


0. II 


0.13 


8 


2 


39 


3 


00 


8 


4-75 


5 


94 


7 


0.16 


0.20 


7 


2 


44 


3 


07 


7 


4.81 


6 


02 


6 


0.21 


0.26 


6 


2 


50 


3 


14 


6 


4.87 


6 


10 


5 


0.26 


033 


5 


2 


56 


3 


21 


5 


4-94 


6 


17 


4 


0.32 


0.40 


4 


2 


61 


3 


28 


4 


5.00 


6 


24 


3 


0.37 


0.46 


3 


2 


67 


3 


35 


3 


5.06 


6 


32 


2 


0.42 


053 


2 


2 


72 


3 


42 


2 


5-i2 


6 


40 


1 


0.47 


0.60 


1 


2 


78 


3 


49 


1 


519 


6 


48 





053 


0.66 





2 


83 


3 


55 





5-25 


6 


55 


O.9989 


0.58 


0.73 


0.0049 


2 


89 


3 


62 


0.9909 


5 3i 


6 


63 


8 


0.63 


0.79 


8 


2 


94 


3 


69 


8 


5-37 


6 


7i 


7 


0.68 


0.86 


7 


3 


00 


3 


76 


7 


5-44 


6 


78 


6 


0.74 


093 


6 


3 


06 


3 


83 


6 


5-5° 


6 


86 


5 


0.79 


0.99 


5 


3 


12 


3 


90 


5 


5-56 


6 


94 


4 


0.84 


1 .06 


4 


3 


18 


3 


98 


4 


5.62 


7 


01 


3 


0.89 


I 13 


3 


3 


24 


4 


05 


3 


569 


7 


09 


2 


o-95 


1. 19 


2 


3 


29 


4 


12 


2 


5-75 


7 


17 


1 


1 .00 


1.26 


1 


3 


35 


4 


20 


1 


5-8i 


7 


25 





1.06 


i-34 





3 


41 


4 


27 





5-8 7 


7 


32 


09979 


1.12 


1.42 


0.9939 


3 


47 


4 


34 


0.9809 


5 94 


7 


40 


8 


1. 19 


1.49 


8 


3 


53 


4 


42 


8 


6.00 


7 


48 


7 


1.25 


i-57 


7 


3 


59 


4 


49 


7 


6.07 


7 


57 


6 


1. 31 


1.65 


6 


3 


65 


4 


56 


6 


6.14 


7 


66 


5 


i-37 


i-73 


5 


3 


7i 


4 


63 


5 


6.21 


7 


74 


4 


1.44 


1. 81 


4 


3 


76 


4 


7i 


4 


6.28 


7 


83 


3 


1-50 


1.88 


3 


3 


82 


4 


78 


3 


6.36 


7 


92 


2 


1-56 


1.96 


2 


3 


88 


4 


85 


2 


6-43 


8 


01 


1 


1 .62 


2.04 


1 


3 


94 


4 


93 


1 


6.50 


8 


10 





1 .69 


2.12 





4 


00 


5 


00 





6-57 


8 


18 


O.9969 


1 75 


2.20 


0.0929 


4 


06 


5 


08 


0.9889 


6.64 


8 


27 


8 


1. 81 


2 . 27 


8 


4 


12 


5 


16 


8 


6.71 


8 


36 


7 


1.87 


2-35 


7 


4 


19 


5 


24 


7 


6.78 


8 


45 


6 


1.94 


2-43 


6 


4 


25 


5 


32 


6 


6.86 


8 


54 


5 


2 .00 


2.51 


5 


4 


3i 


5 


39 


5 


6-93 


8 


63 


4 


2.06 


2.58 


4 


4 


37 


5 


47 


4 


7.00 


8 


72 


3 


2. 11 


2.62 


3 


4 


44 


5 


55 


3 


7.07 


8 


80 


2 


2.17 


2.72 


2 


4 


50 


5 


63 


2 


7-i3 


8 


88 


1 


2.22 


2-79 


1 


4 


56 


5 


7i 


1 


7. 20 


8 


96 





2.28 


2.86 





4 


62 


5 


78 





7.27 


9.04 



2l8 



AIR, WATER, AND FOOD 



TABLE X. — (Continued) 

PERCENTAGE OF ALCOHOL 





Per cent 


Per cent 




Per cent 


Per cent 




Per cent 


Per cent 


Sp. gr. 


alcohol 


alcohol 


Sp.gr. 


alcohol 


alcohol 


Sp. gr. 


alcohol 


alcohol 


i5°-5 C. 


by 


by 


IS°.5 C. 


by 


by 


I5°.5 C. 


by 


by 




weight. 


volume. 




weight. 


volume. 




weight. 


volume. 


O.9879 


7 33 


9 13 


5 


IO.46 


12.96 


2 


13-77 


16.98 


8 


7 


40 


9.21 


4 


IO-54 


13 


•05 


I 


13 


.85 


17.08 


7 


7 


47 


9.29 


3 


IO.62 


13 


•15 


O 


13 


.92 


17.17 


6 


7 


53 


9-37 


2 


IO.69 


13 


.24 










5 


7 


60 


9-45 


1 


IO.77 


13 


•34 


O.9789 


14 


00 


17.26 


4 


7 


67 


9-54 





10.85 


13 


43 


8 


14 


09 


17-37 


3 


7 


73 


9.62 










7 


14 


18 


17.48 


2 


7 


80 


9.70 


0.9829 


IO.92 


13 


52 


6 


14 


27 


17-59 


1 


7 


87 


9.78 


8 


11 .00 


13 


62 


5 


14 


36 


17.70 





7 


93 


9.86 


7 


11.08 


13 


72 


4 


14 


45 


17.81 










6 


II. 15 


13 


81 


3 


14 


55 


17.92 


0.9869 


8 


00 


9 95 


5 


II.23 


13 


90 


2 


14 


64 


18.03 


8 


8 


07 


10.03 


4 


II. 31 


13 


99 


1 


14 


73 


18.14 


7 


8 


•14 


10.12 


3 


11.38 


14 


09 





14 


82 


18.25 


6 


8 


.21 


10.21 


2 


II.46 


14 


18 










5 


8 


.29 


10.30 


1 


H-54 


14 


27 


0.9779 


14 


90 


18.36 


4 


8 


•36 


10.38 





11 .62 


14 


37 


8 


15 


00 


18.48 


3 


8 


•43 


10.47 










7 


15 


08 


18.58 


2 


8 


•So 


10.56 


0.9819 


11.69 


14 


46 


6 


15 


17 


18.68 


1 


8 


•57 


10.65 


8 


11.77 


14 


56 


5 


15 


25 


18.78 





8 


.64 


10.73 


7 


n.85 


14 


65 


4 


15 


33 


18.88 


0.9859 

8 
7 


8 

8 
8 


7i 

79 
86 


10.82 

10.91 
11 .00 


6 

5 
4 


11.92 

12.00 
12.08 


14 
14 
14 


74 
84 
93 


3 
2 

1 


15 
15 
15 


42 
50 
58 


18.98 
19.08 
19.18 


6 


8 


93 


11.08 


3 
2 


12.15 
12.23 
12.31 
12.38 

12.46 


15 
15 
15 
15 

15 


02 
12 





15 


67 


19.28 


5 
4 
3 
2 


9 
9 
9 
9 


00 
07 

14 

21 


11. 17 
11.26 

n-35 
11.44 


1 


O.9809 


21 

30 

40 


O.9769 

8 

7 
6 


15 

15 
15 
16 


75 

83 
92 
00 


19 39 

19.49 

19-59 
19.68 


1 



9 
9 


29 
36 


11 .52 
11. 61 


8 

7 


12.54 
12.62 


15 
15 


49 

58 


5 
4 


16 
16 


08 
15 


19.78 
19.87 


0.9849 


9 


43 


11.70 


6 


12.69 


15 


68 


3 


16 


23 


19.96 


8 


9 


5° 


11.79 


5 


12.77 


15 


77 


2 


16 


31 


20.06 


7 


9 


57 


11.87 


4 


12.85 


15 


86 


1 


16. 


38 


20.15 


6 


9 


64 


11.96 


3 


12.92 


15 


96 





16. 


46 


20.24 


5 


9 


7i 


12.05 


2 


13.00 


16 


05 










4 


9 


79 


12.13 


1 


13.08 


16 


15 


0-9759 


16. 


54 


20.33 


3 


9 


86 


12.22 





I3-I5 


16. 


24 


8 


16. 


62 


20.43 


2 


9 


93 


12.31 










7 


16. 


69 


20.52 


1 


10 


00 


12.40 


0.9799 


13 23 


16 


33 


6 


16. 


77 


20.61 





10 


08 


12.49 


8 


I33I 


16. 


43 


5 


16. 


85 


20.71 










7 


13-38 


16. 


52 


4 


16. 


92 


20.80 


0.9839 


10 


15 


12.58 


6 


13.46 


16. 


61 


3 


17. 


00 


20.89 


8 


10 


23 


12.68 


5 


13-54 


16. 


7o 


2 


17- 


08 


20.99 


7 


10 


3i 


12.77 


4 


13.62 


16. 


80 


1 


17- 


17 


21.09 


6 


10 


38 


12.87 


3 


13.69 


16 


89 





1725 


21.19 






APPENDIX A 
TABLE X. — {Continued) 

PERCENTAGE OF ALCOHOL 



219 





Per cent 


Per cent 




Per cent 


Per cent 




Per cent 


Per cent 


Sp. gr. 


alcohol 


alcohol 


Sp. gr. 


alcohol 


alcohol 


Sp. gr. 


alcohol 


alcohol 


I5°.5 C. 


by 


by 


I5°.5 C. 


by 


by 


I5°.5C. 


by 


by 




weight. 


volume. 




weight. 


volume. 




weight. 


volume. 


0.9749 


17 33 


21.29 


6 


20.00 


24.48 


3 


22.62 


27-59 


8 


17 


42 


20.39 


5 


20.08 


24 


58 


2 


22.69 


27.68 


7 


17 


50 


21.49 


4 


20.17 


24 


68 


I 


22.77 


27.77 


6 


17 


58 


21.59 


3 


20.25 


24 


78 


O 


22.85 


27.86 


5 


17 


67 


21 .69 


2 


20.33 


24 


88 








4 


17 


75 


21-79 


1 


20.42 


24 


98 


O.9679 


22.92 


27 95 


3 


17 


S3 


21.89 





20.50 


25 


07 


8 


23.00 


28 . 04 


2 


17 


92 


21.99 










7 


23.08 


28.13 


1 


18 


00 


22.09 


0.9709 


20.58 


25 


17 


6 


23 15 


28.22 





18 


08 


22.18 


8 


20.67 


25 


27 


5 


23-23 


28.31 










7 


20.75 


25 


37 


4 


23-31 


28.41 


0-9739 


18 


15 


22.27 


6 


20 . 83 


25 


47 


3 


23-38 


28.50 


8 


18 


23 


22.36 


5 


20.92 


25 


57 


2 


23.46 


28.59 


7 


18 


31 


22.46 


4 


2I.OO 


25 


67 


1 


23-54 


28.68 


6 


18 


38 


22.55 


3 


21.08 


25 


76 





23.62 


28.77 


5 


18 


46 


22.64 


2 


21.15 


25 


86 








4 


18 


54 


22-73 


1 


21.23 


25 


95 


0.9669 


2369 


28.86 


3 


18 


62 


22.82 





21.31 


26 


04 


8 


23-77 


28.95 


2 


18 


69 


22.92 










7 


2385 


29.04 


1 


18 


77 


23.OI 


0.9699 


21.38 


26 


13 


6 


23.92 


29.13 





18 


85 


23.IO 


8 


21.46 


26 


22 


5 


24.00 


29.22 










7 


21-54 


26 


31 


4 


24.08 


29.31 


09729 


18 


92 


23.19 


6 


21.62 


26 


40 


3 


2415 


29.40 


8 


19 


00 


23.28 


5 


21 .69 


26 


49 


2 


24.23 


29.49 


7 


19 


08 


23.38 


4 


21-77 


26 


58 


1 


24-31 


29.58 


6 


19 


17 


23.48 


3 


21.85 


26 


67 





24.38 


29.67 


5 


19 


25 


2358 


2 


21.92 


26 


77 








4 


19 


33 


23.68 


1 


22.CO 


26 


86 


0.9659 


24.46 


29.76 


3 


19 


42 


23.78 





22.08 


26 


95 


8 


24-54 


29.86 


2 


19 


50 


23-88 










7 


24.62 


29-95 


1 


19 


58 


23.98 


0.9689 


22.15 


27 


04 


6 


24.69 


30.04 





19 


67 


24.08 


8 


22 . 23 


27 


13 


5 


24.77 


30.13 










7 


22.31 


27 


22 


4 


24.85 


30.22 


O.0719 


19 


75 


24.18 


6 


22.38 


27 


3i 


3 


24.92 


30-31 


8 


19 


83 


24.28 


5 


22.46 


27 


40 


2 


25.00 


30.40 


7 


19.92 


24-38 


4 


22-54 


27.49 









220 



AIR, WATER, AND FOOD 



TABLE XI 

EXTRACT IN WINE 

Per cent by Weight 
(According to Windisch) 



Sp.gr. 


Ex- 


Sp.gr. 


Ex- 


Sp. gr. 


Ex- 


Sp.gr. 


Ex- 


Sp.gr. 


Ex- 


Sp. gr. 


Ex- 




tract. 




tract. 




tract. 




tract. 




tract. 




tract. 


I.OOOO 


0.00 


1 . 0200 


5.17 


1 . 0400 


10.35 


1 . 0600 


15.55 


1.0800 


20.78 


1. 1000 


26.04 


i. coos 


0.13 


1 . 0205 


530 


1.0405 


10.48 


1 . 0605 


15-68 


1.0805 


20.91 


1. 1005 


26.17 


I.OOIO 


0.26 


1. 0210 


5-43 


1. 0410 


10.61 


1. 0610 


15.81 


1. 0810 


21.04 


I.IOIO 


26.30 


1. 0015 


0.39 


1. 0215 


5.56 


1. 0415 


10.74 


1. 0615 


15.94 


1. 0815 


21.17 


1.1015 


26.43 


1.0020 


0.52 


1 . 0220 


569 


1 . 0420 


10.87 


1 . 0620 


16.07 


1.0820 


21.31 


1 . 1020 


26.56 


1.0025 


0.64 


1.0225 


582 


1.0425 


11.00 


1.0625 


16.21 


1.0825 


21.44 


1 . 1025 


26.70 


1.0030 


0.77 


1.0230 


594 


1.0430 


11. 13 


1.0630 


i6.33 


1.0830 


21.57 


1 . 1030 


26.83 


1.0035 


0.90 


1.0235 


6.07 


1043s 


11.26 


10635 


16.47 


1.083S 


21.70 


1. 1035 


26.96 


1.0040 


1.03 


1 . 0240 


6.20 


1 . 0440 


11.39 


1 . 0640 


16.60 


1.0840 


21.83 


1 . 1040 


27.00 


I . 0045 


1. 16 


1.024s 


6.33 


1.0445 


11.52 


1 . 0645 


16.73 


1.0845 


21.96 


1 -1045 


27.22 


1.0050 


1.29 


1.0250 


6?46 


1.0450 


11.65 


1 . 0650 


16.86 


1.0850 


22.09 


I . 1050 


27.35 


1.0055 


1.42 


1.0255 


6.59 


1.045s 


11.78 


1.065S 


16.99 


10855 


22.22 


1. 1055 


27.49 


I . 0060 


155 


1 . 0260 


6.72 


1.0460 


11. 91 


1 . 0660 


17.12 


1.0860 


22.36 


1. 1060 


27.62 


1.0065 


1.68 


1.0265 


6.85 


1.0465 


12.04 


1 . 0665 


1725 


1.0865 


22.49 


1 . 1065 


27-75 


1.0070 


1. 81 


1 . 0270 


'6 : 98 


.1 ■ 0470 


12.17 


1 . 0670 


17.38 


1 . 0870 


22.62 


1. 1070 


27.88 


1.0075 


1 94 


1.0275 


7Tn 


1.0475 


12.30 


1.067S 


I7.5I 


1.087s 


22.75 


1. 1075 


28. or 


1.0080 


2.07 


1 . 0280 


7*24 


1 . 0480 


12.43 


1.0680 


17.64 


1.0880 


22.88 


1. 1080 


28. is 


I . 0085 


2.19 


1.0285 


J. 37 


1.0485 


12.56 


1.0685 


17-77 


1.0885 


23.01 


1 . 1085 


28.28 


1.0090 


2.32 


1 . 0290 


Y'.50 


1 . 0490 


12.69 


1 . 0690 


17.90 


1 . 0890 


2314 


1. 1090 


28.41 


1.0095 


2.45 


1.0295 


763 


1.0495 


12.82 


1.0695 


18.03 


1.0895 


2328 


1. 1095 


28.54 


I . 0100 


2.58 


1.0300 


7-76 


1.0500 


12.95 


1.0700 


18.16 


1 . 0900 


23.41 


I.IIOO 


28.67 


I . 0105 


2.71 


1. 0305 


7.89 


1. 0505 


1308 


1.0705 


18.30 


1.0905 


23.54 


1.1105 


28.81 


I. OIIO 


2.84 


1. 0310 


8.02 


1. 0510 


1321 


1. 0710 


18.43 


1. 0910 


23.67 


I.IIIO 


28.94 


1.0115 


2.97 


1. 0315 


8.14 


1. 0515 


13-34 


1. 0715 


18.56 


1-0915 


23.80 


1. HIS 


29.07 


I. 0120 


310 


1.0320 


8.27 


1.0520 


13-47 


1.0720 


18.69 


1.0920 


23-93 


1.1120 


29.20 


I. 0125 


323 


1.0325 


8.40 


10525 


1360 


1.0725 


18.82 


1.0925 


24.07 


1.1125 


29.33 


I. 0130 


3.36 


10330 


8.53 


1.0530 


13.73 


1.0730 


18.95 


1 . 0930 


24.20 


1.1130 


29-47 


I. 0135 


3-49 


1.0335 


8.66 


1-0535 


13-86 


I.0735 


19.08 


1 0935 


2433 


I.H35 


29.60 


I. 0140 


3-62 


1.0340 


8.79 


1 . 0540 


13.99 


1.0740 


19.21 


1 . 0940 


24.46 


1.1140 


29.73 


I. 0145 


3-75 


1.0345 


8.92 


1.0545 


14.12 


1.0745 


1934 


1.0945 


2459 


I.H45 


29.86 


I. 0150 


3.87 


1.0350 


905 


1.0550 


14.25 


1.0750 


19-47 


1.0950 


24.72 


1.1150 


29.99 


I. 0155 


4.00 


1.0355 


9.18 


I.OS55 


14.38 


I.0755 


19.60 


1. 0955 


24.85 


I.H55 


30.13 


I. 0160 


4.13 


1 . 0360 


9-31 


1.0560 


14.51 


1 . 0760 


1973 


1 . 0960 


2499 






I. 0165 


4.26 


10365 


9-44 


1.056s 


14.64 


1.0765 


19.86 


1 . 0965 


25.12 






I. 0170 


4-39 


1.0370 


9-57 


1.0570 


14.77 


1.0770 


20.00 


1 . 0970 


25.25 






10T75 


4-52 


1.0375 


9- 70 


1. 0575 


14.90 


1.0775 


20.12 


10975 


25.38 






1. 0180 


4.65 


1.0380 


9.83 


1.0580 


15.03 


1 . 0780 


20.26 


1.0980 


25.51 






1. 0185 


4.78 


1.0385 


996 


1.058S 


15- 16 


1.0785 


20.39 


1.0985 


25.64 






1. 0190 


4-91 


1.0390 


10.09 


1.0590 


1529 


1 . 0790 


20.52 


1 . 0990 


25-78 






1. 0195 


5.04 


I. 0395 


10.22 


1. o59S 


15.42 


1.0795 


20.65 


1 0995 


25.91 







APPENDIX A 



221 



TABLE XII 



TABLE FOR REDUCING SUGAR CONDENSED FROM THAT OF 
MUNSON AND WALKER 

(Expressed in milligrams) 














12 

°o 

So 


aj 
w 

2 
p 


bO 

w 
u 

> 


*5 


H 

&6 


O 




t— 1 







10 


4-0 


4-5 


4.0 


5.9 


15 


6.2 


6.7 


7.5 


99 


20 


8.3 


8.9 


10.9 


13.8 


25 


10.5 


n. 2 


14.4 


17.8 


30 


12.6 


13-4 


17.8 


21.8 


35 


14.8 


15.6 


21.3 


25-7 


40 


16.9 


17.8 


24.8 


297 


45 


19. 1 


20.1 


28.2 


337 


5o 


21.3 


22.3 


31 -7 


37.6 


55 


23.5 


24.6 


35- 1 


41.6 


60 


25.6 


26.8 


38.6 


45-6 


65 


27.8 


29.1 


42.1 


495 


70 


30.0 


313 


45-5 


535 


75 


32.2 


33-6 


49-0 


57-5 


80 


34-4 


359 


52.5 


61.4 


85 


36.7 


38.2 


56.0 


654 


90 


38.9 


40.4 


59-4 


693 


95 


41. 1 


42.7 


62.9 


733 


100 


433 


45.o 


66.4 


77-3 


105 


45-5 


47-3 


69.8 


81.2 


no 


47-8 


49-6 


73-3 


85.2 


115 


50.0 


51.9 


76.8 


89.2 


120 


52-3 


54-3 


80.3 


93- 1 


125 


54-5 


56.6 


83.8 


971 


130 


56.8 


58.9 


87.3 


IOI.O 


135 


59-0 


61.2 


90.8 


105.0 


140 


61.3 


63.6 


942 


109.0 


145 


63.6 


65-9 


977 


112. 9 


150 


65-9 


68.3 


101.2 


116. 9 


155 


68.2 


70.6 


104.7 


120.8 


160 


70.4 


73-0 


108.2 


124.8 


165 


72.8 


75-3 


ill. 7 


128.8 


170 


75.1 


77-7 


115 2 


132.7 


175 


77-4 


80.1 


118. 7 


136.7 


180 


79-7 


82.5 


122.2 


140.6 


185 


84.2 


849 


125-7 


1446 


190 


843 


87.2 


129.2 


148.6 


195 


86.7 


89.6 


132.7 


152.5 


200 


89.0 


92.0 


1362 


156.5 


205 


91.4 


945 


139-7 


160.4 


210 


93-7 


96.9 


143.2 


164.4 


215 


96.1 


993 


146.7 


168.3 


220 


98.4 


101.7 


150.2 


172.3 


225 


100.8 


104.2 


153 7 


176.2 


230 


103.2 


106.6 


157.2 


180.2 


235 


105.6 


109. 1 


160.7 


184.2 


240 


108.0 


in. 5 


164.3 


188. 1 


245 


no. 4 


114. 


167.8 


192. 1 


250 


112. 8 


116. 4 


I7I- 3 


196.0 


255 


115. 2 


118. 9 


174-8 


200.0 



<u 






q 




I© 


2 


a 
00 
3 




s 


3 


Q 


C 
> 


"£0 


*6 







i— 1 







260 


117. 6 


121. 4 


178.3 


203.9 


265 


120.0 


1239 


181. 9 


207.9 


270 


122.5 


I26.4 


185.4 


211. 8 


275 


124.9 


128.9 


188.9 


215.8 


280 


1273 


I3I-4 


192.4 


219.7 


285 


129.8 


1339 


196.0 


223.7 


290 


132.3 


136.4 


199 .5 


227.6 


295 


134.7 


138.9 


203.0 


231.6 


300 


137-2 


141. 5 


206.6 


235-5 


305 


139-7 


I44-Q 


210. 1 


239.5 


310 


142.2 


146.6 


2137 


2435 


315 


144.7 


149- 1 


217.2 


247-4 


320 


147-2 


151. 7 


220.7 


251-3 


325 


149-7 


1543 


224.3 


2553 


330 


152.2 


156.8 


227.8 


2593 


335 


154.7 


1594 


2314 


263.2 


340 


157-3 


162.0 


234-9 


267.1 


345 


159-8 


164.6 


238.5 


271. 1 


350 


162.4 


167.2 


242.0 


2750 


355 


164.9 


169.8 


245.6 


279.0 


360 


167.5 


172.5 


249.1 


282.9 


365 


170. 1 


175. 1 


252.7 


286.9 


370 


172.7 


177.7 


256.2 


290.8 


375 


175-3 


180.4 


2598 


294.8 


380 


1779 


183.0 


263.4 


298.7 


385 


180.5 


185.7 


266.9 


302.7 


390 


183. 1 


188.4 


270.5 


306.6 


395 


185.7 


191. 


274-0 


310.6 


400 


188.4 


1937 


277.6 


314-5 


405 


191. 


196.4 


281. 1 


318.5 


410 


1937 


199- 1 


284.7 


322.4 


415 


196.3 


201.8 


288.3 


326.3 


420 


199 


204.6 


291.9 


330.3 


425 


201.7 


207.3 


295-4 


3342 


430 


204.4 


210.0 


299.0 


338.2 


435 


207.1 


212.8 


302.6 


342.1 


440 


209.8 


2155 


306.2 


346.1 


445 


212.5 


218.3 


309-7 


350.0 


450 


2152 


221. 1 


313 3 


3539 


455 


218.0 


223.9 


316.9 


357-9 


460 


220.7 


226.7 


320.5 


361.8 


465 


223.5 


229.5 


324- 1 


365.8 


470 


226.2 


232.3 


327-7 


369-7 


475 


229.0 


235.1 


331.3 


3737 


480 


231.8 


2379 


3348 


377-6 


485 


234-6 


240.8 


338.4 


381.5 


490 


237-4 


2436 


342.0 


385.5 



222 



AIR, WATER, AND FOOD 



TABLE XIII 



EXTRACT IN BEER-WORT 

(According to Schultz and Ostermann) 



Specific 


Extract. S 


pecific 


Extract. Si 


jecific 


Extract. S] 


)ecific 


Extract. 


gravity at 


Per cent gn 


ivity at 


Per cent gra 


vity at 


Per cent gra 


vity at 


Per cent 


15° C. 


by weight. j 


5°C. 


by weight. 1 


5°C. 


by weight. 1 


5°C. 


by weight. 


I . oooo 


O.OO 1 


0235 


6.07 I 


0470 


11.89 1 


0705 


17-59 


I . 0005 


O 


13 1 


0240 


6 


19 1 


0475 


12 


OI I 


0710 


17.70 


I .0010 


O 


26 1 


0245 


6 


3i 1 


0480 


12 


14 I 


0715 


17.81 


I. 0015 


O 


39 1 


0250 


6 


44 1 


0485 


12 


26 I 


0720 


17-93 


I .0020 


O 


52 1 


0255 


6 


58 1 


0490 


12 


38 I 


0725 


18.04 


I .0025 


O 


66 1 


0260 


6 


71 1 


0495 


12 


50 I 


0730 


18.15 


I . 0030 


O 


79 1 


0265 


6 


85 1 


0500 


. 12 


63 I 


0735 


18.26 


1.003s 


O 


92 1 


0270 


6 


99 1 


0505 


12 


75 1 


0740 


18.38 


I . 0040 


1 


05 1 


0275 


7 


12 1 


0510 


12 


87 1 


0745 


18.49 


1.0045 


I 


18 1 


0280 


7 


26 1 


05I5 


12 


99 1 


0750 


18.59 


I .0050 


I 


3i 1 


0285 


7 


37 1 


0520 


13 


12 1 


0755 


18.70 


* -0055 


1 


44 1 


0290 


7 


48 1 


0525 


13 


24 1 


0760 


18.81 


I . 0060 


I 


56 1 


0295 


7 


60 1 


0530 


13 


36 1 


0765 


18.91 


I .0065 


I 


69 1 


0300 


7 


71 1 


0535 


13 


48 1 


0770 


19.02 


J .0070 


I 


82 1 


0305 


7 


82 1 


0540 


13 


61 1 


0775 


19.12 


1.0075 


1 


95 1 


0310 


7 


93 1 


0545 


13 


73 1 


0780 


19.23 


I . 0080 


2 


07 1 


0315 


8 


04 1 


0550 


13 


86 1 


0785 


19-33 


1.0085 


2 


20 1 


0320 


8 


16 1 


0555 


13 


98 1 


0790 


19.44 


I . 0090 


2 


33 1 


0325 


8 


27 1 


0560 


M 


11 1 


0795 


19.56 


1.0095 


2 


46 1 


0330 


8 


40 1 


O505 


14 


23 1 


0800 


19.67 


I .0100 


2 


58 1 


0335 


8 


53 1 


0570 


14 


36 1 


0805 


19.79 


I. 0105 


2 


71 1 


0340 


8 


67 1 


0575 


14 


49 1 


0810 


19.91 


I .0110 


2 


84 1 


0345 


8 


80 1 


0580 


14 


62 1 


0815 


20.03 


1.0115 


2 


97 1 


0350 


8 


94 1 


0585 


14 


75 1 


0820 


20.14 


I .0120 


3 


10 1 


0355 


9 


07 1 


0590 


14 


89 1 


0825 


20.26 


I. 0125 


3 


23 1 


0360 


9 


21 1 


°595 


15 


02 1 


0830 


20.37 


I. 0130 


3 


35 1 


0365 


9 


34 1 


0600 


15 


14 1 


0835 


20.48 


I 0135 


3 


48 1 


0370 


9 


45 1 


0605 


15 


25 1 


0840 


20.59 


I. 0140 


3 


61 1 


0375 


9 


57 1 


0610 


15 


36 1 


0845 


20.70 


I. 0145 


3 


74 1 


0380 


9 


69 1 


0615 


15 


47 1 


0850 


20.81 


I. 0150 


3 


87 1 


038S 


9 


81 1 


0620 


15 


58 1 


0855 


20.93 


I. 0155 


4 


00 1 


0390 


9 


92 1 


0625 


15 


69 1 


0860 


21 .06 


I .0160 


4 


13 1 


0395 


10 


04 1 


0630 


15 


80 1 


0865 


21.19 


1.016s 


4 


26 1 


04OO 


10 


16 1 


0635 


15 


92 1 


0870 


21-33 


I .0170 


4 


39 1 


0405 


10 


27 1 


0640 


16 


03 1 


0875 


21-43 


:1.017s 


4 


53 1 


0410 


10 


40 1 


0645 


16 


14 1 


0880 


21-54 


I. 0180 


4 


66 1 


0415 


10 


52 1 


0650 


16 


25 1 


0885 


21 .64 


1.0185 


4 


79 1 


0420 


10 


65 1 


0655 


16 


37 1 


0890 


21-75 


I .0190 


4 


93 1 


0425 


10 


'7 1 


0660 


16 


50 1 


0895 


21.86 


1.019s 


5 


06 1 


0430 


10 


90 1 


0665 


16 


62 1 


0900 


21.98 


1.0200 


5 


20 1 


0435 


11 


03 1 


0670 


16 


74 1 


0905 


22.08 


1.0205 


5 


33 1 


0440 


11 


15 1 


0675 


16 


86 1 


0910 


22.19 


I. 0210 


5 


45 1 


0445 


11 


28 1 


0680 


16 


99 1 


09I5 


22.30 


I. 0215 


5 


57 1 


0450 


11 


40 1 


0685 


17 


11 1 


0920 


22.41 


I .0220 


5 


70 1 


0455 


11 


53 1 


0690 


17 


23 1 


0925 


22.52 


I .0225 


5 


82 1 


0460 


11 


65 1 


0695 


17 


35 1 


0930 


22.63 


1.0230 


5 


94 1 


0465 


11 


77 1 


0700 


17 


48 1 


0935 


22.73 



APPENDIX A 



223 



TABLE XIII. — (Continued) 

EXTRACT IN BEER-WORT 

(According to Schultz and Ostermann) 



Specific 


Extract. 


Specific 


Extract. 


Specific 


Extract. 


Specific 


Extract. 


gravity at 


Per cent 


gravity at 


Per cent 


gravity at 


Per cent 


gravity at 


Per cent 


15° C. 


by weight. 


15° C. 


by weight. 
24-53 


15° C. 


by weight. 


15° C. 


by weight. 


I . 0940 


22.84 


I . 1020 


I . I 100 


26.27 


I. I 180 


27.88 


I 


•0945 


22 


94 


1. 1025 


24.64 


I.1105 


26.37 


I.H85 


27.98 


I 


0950 


23 


05 


I . 1030 


24.74 


I.IIIO 


26.48 


I .1190 


28.09 


I 


0955 


23 


16 


1 I035 


24.85 


1. iiiS 


26.58 


I.1195 


28.19 


I 


0960 


23 


27 


I . 1040 


24.96 


1 . 1 1 20 


26.68 


I. I200 


28.28 


I 


0965 


23 


37 


1 • 1045 


25.07 


1.1125 


26. 79 


1-1205 


28.38 


I 


0970 


23 


48 


I . 1050 


25.18 


1-1130 


26.89 


I .I2IO 


28.48 


I 


0975 


23 


59 


1 -IQ55 


25.29 


I-H35 


26.99 


I.1215 


28.58 


I 


0980 


23 


69 


I . 1060 


25.40 


1.1140 


27.09 


I .1220 


28.68 


I 


0985 


23 


80 


1 ■ 1065 


25-50 


1.1145 


27.19 


1. 1225 


28.78 


I 


0990 


23 


90 


I . 1070 


25.61 


1-1150 


27.29 


1. 1230 


28.88 


I 


0995 


24 


01 


1. 1075 


25-71 


III55 


27.38 


1-1235 


28.98 


I 


IOOO 


24 


11 


I . 1080 


25.82 


1 . 1 160 


27.48 


1 . 1 240 


29.08 


I 


1005 


24 


21 


1 . 1085 


25-93 


1-1165 


27.58 


1. 1245 


29.18 


I 


IOIO 


24 


32 


I . 1090 


26.05 


1.1170 


27.68 


1-1250 


29.28 


I 


1015 


24 


43 


I . 1095 


26.16 


1. "75 


27.78 


1 -1255 


29.38 



224 



AIR, WATER, AND FOOD 











LOGARITHMS 


OF 


NUMBERS 












Natural 
num- 





1 


2 


3 


4 


5 


6 


7 


8 


9 


Proportional parts. 


bers. 


4 
4 
3 
3 
3 


2 

8 
8 
7 
6 
6 


3 

12 
11 

10 
10 
9 


4 5 6 

17 21 25 
15 19 23 
14 17 21 
13 l6 19 
12 15 18 


789 


IO 
II 
12 
13 
14 


0000 
0414 
0792 

ii39 
146 1 


0043 

0453 
0828 

"73 
1492 


0086 
0492 
0864 
1206 
1523 


0128 

0531 
0899 
1239 

1553 


0170 
0569 

0934 
1271 

1584 


0212 
0607 
0969 

I303 
1614 


0253 
0645 
1004 

1335 
1644 


0294 
0682 
1038 
1367 
1673 


0334 
0719 
1072 

1399 
1703 


0374 
0755 
1 106 

I430 

1732 


29 33 37 
263034 
24 28 31 
23 26 29 
21 24 27 


15 

16 

17 
18 

19 


1761 
2041 
2304 

2553 
2788 


1790 
2068 
2330 
2577 
2810 


1818 

2095 

2355 
2601 

2833 


1847 
2122 
2380 
2625 
2856 


1875 
2148 
2405 
2648 
2878 


1903 

2175 
2430 
2672 
2900 


1931 

2201 

2455 
2695 
2923 


1959 

2227 
2480 
2718 
2945 


1987 
2253 
2504 
2742 
2967 


2014 
2279 

2529 
2765 
2989 


3 
3 
2 
2 

2 


6 

5 
5 
5 
4 


8 
8 
7 
7 
7 


II 14 17 
II 13 l6 
10 12 15 

9 12 14 
9 11 13 


20 22 25 
18 21 24 
17 20 22 
16 19 21 
16 18 20 


20 
21 
22 

23 
24 


3010 
3222 

3424 
3617 
3802 


3032 
3243 
3444 
3636 
3820 


3054 
3263 
3464 
3655 
3838 


3075 
3284 
3483 
3674 
3856 


3096 
3304 
3502 
3692 
3874 


3118 
3324 
3522 

3711 
3892 


3139 
3345 
354i 
3729 
3909 


3160 

3365 
356o 
3747 
3927 


3181 

3385 
3579 
3766 

3945 


3201 
3404 
3598 
3784 
3962 


2 
2 
2 
2 
2 


4 
4 
4 
4 

4 


6 
6 
6 
6 

5 


8ll 13 

8 10 12 
8 10 12 
7 9 11 
7 9 11 


IS 17 19 

14 16 18 
14 15 17 
13 15 17 
12 14 16 


25 
26 

27 
28 

29 


3979 
4150 
4314 
4472 
4624 


3997 
4166 

4330 
4487 

4639 


4014 
4183 
4346 
4502 
4654 


4031 
4200 
4362 
4518 
4669 


4048 
4216 
4378 
4533 
4683 


4065 

4232 
4393 
4548 
4698 


4082 
4249 
4409 
4564 
4713 


4099 
4265 
4425 
4579 
4728 


4116 
4281 
4440 
4594 
4742 


4133 

4298 
4456 
4609 
4757 


2 
2 
2 
2 

I 


3 
3 
3 
3 

3 


5 
5 
5 
5 
4 


7 9 10 
7 8 10 
689 
689 
679 


12 14 15 
11 13 15 
11 13 14 
11 12 14 
10 12 13 


30 
31 
32 

33 
34 


477i 
4914 

5051 
5185 
5315 


4786 
4928 
5065 
5198 
5328 


4800 
4942 

5079 
5211 
5340 


4814 
4955 
5092 
5224 
5353 


4829 
4969 
5io5 
5237 
5366 


4843 
4983 
5ii9 
5250 
5378 


4857 
4997 
5132 
5263 
539i 


4871 
501 1 

5145 
5276 

5403 


4886 
5024 
5159 
5289 
54i6 


4900 
5038 
5172 
53°2 
5428 


I 
I 
I 

I 
I 


3 
3 
3 
3 

3 


4 
4 
4 
4 
4 


679 
678 
5 7 8 
568 
568 


to 11 13 

CO II 12 
9 II 12 
9 10 12 
9 10 ir 


35 
36 
37 
38 
39 


544i 
5563 
5682 

5798 
59 11 


5453 
5575 
5694 
5809 
5922 


5465 
5587 
5705 
5821 
5933 


5478 
5599 
5717 
5832 
5944 


549° 
5611 

5729 
5843 
5955 


5502 
5623 
5740 
5855 
5966 


5514 

5635 
5752 
5866 
5977 


5527 
5647 
5763 
5877 
5988 


5539 
5658 

5775 
5888 

5999 


555i 

5670 
5786 

5899 
6010 


I 
I 

I 
I 
I 


2 
2 
2 
2 
2 


4 
4 
3 
3 
3 


567 
567 
567 
567 
4 5 7 


9 10 II 
8 10 11 
8 9 10 
8 9 10 
8 9 10 


40 
4i 
42 
43 
44 


6021 
6128 
6232 
6335 
6435 


6031 
6138 
6243 
6345 
6444 


6042 
6149 
6253 
6355 
6454 


6053 
6160 
6263 

6365 
6464 


6064 
6170 
6274 

6375 
6474 


6075 
6180 
6284 
6385 
6484 


6085 
6191 
6294 
6395 
6493 


6096 
6201 
6304 
6405 
6503 


6107 
6212 
6314 
6415 
6513 


6117 
6222 

6325 
6425 
6522 


I 
I 
I 

I 
I 


2 
2 
2 
2 
2 


3 
3 
3 
3 
3 


4 5 6 
4 5 6 
4 5 6 
4 5 6 
4 5 6 


8 9 10 
789 
789 
789 
789 


45 
46 

47 
48 

49 


6532 
6628 
6721 
6812 
6902 


6542 
6637 
6730 
6821 
691 1 


655i 
6646 

6739 
6830 
6920 


6561 
6656 
6749 
6839 
6928 


6571 
6665 
6758 
6848 
6937 


6580 
6675 
6767 
6857 
6946 


6590 
6684 
6776 
6866 
6955 


6599 
6693 

6785 
6875 
6964 


6609 
6702 
6794 
6884 
6972 


6618 
6712 
6803 

6893 
6981 


I 

I 
I 
I 

I 


2 

2 
2 
2 
2 


3 
3 
3 
3 
3 


4 5 6 
4 5 6 

4 5 5 
4 4 5 
4 4 5 


789 
7 7 8 
678 
678 
6 7 8 


5o 
5i 
52 
53 
54 


6990 
7076 
7160 
7243 
7324 


6998 
7084 
7168 
7251 
7332 


7007 

7093 
7177 

7259 
734o 


7016 
7101 

7185 
7267 
7348 


7024 
7110 
7i93 

7275 
7356 


7033 
7118 
7202 
7284 
7364 


7042 
7126 
7210 
7292 
7372 


7050 

7135 
7218 
7300 
738o 


7059 
7143 
7226 
73o8 
7388 


7067 
7152 
7235 
73i6 
7396 


I 
I 
I 

I 
I 


2 

2 
2 
2 
2 


3 
3 

2 

2 
2 


3 4 5 
3 4 5 
3 4 5 
3 4 5 
3 4 5 


6 7 8 
6 7 8 
6 7 7 
667 
667 



APPENDIX A 



225 











LOGARITHMS 


OF 


NUMBERS 




Natural 




















Proportic 


jnal parts. 


num- 





1 


2 


3 


4 


5 


6 


7 


8 


9 




bers. 




7412 


7419 










7459 




12 3 4 


56789 


55 


7404 


7427 


7435 


7443 


7451 


7466 


7474 1223 


45567 


56 


7482 


7490 


7497 


7505 


75i3 


7520 


7528 


7536 


7543 


7551 1223 


45567 


57 


7559 


7566 


7574 


7582 


7589 


7597 


7604 


7612 


7619 


7627 1223 


45567 


58 


7634 


7642 


7649 


7657 


7664 


7672 


7679 


7686 


7694 


7701 1 1 2 3 


44567 


59 


7709 


7716 


7723 


773i 


7738 


7745 


7752 


7760 


7767 


7774 1 1 2 3 


44567 


60 


7782 


7789 


7796 


7803 


7810 


7818 


7825 


7832 


7839 


7846 1 2 3 


4 4 5 6 6 


61 


7853 


7860 


7868 


7875 


7882 


7889 


7896 


7903 


7910 


79 J 7 1 1 2 3 


4 4 5 6 6 


62 


7924 


793i 


7938 


7945 


7952 


7959 


7966 


7973 


7980 


7987 1 1 2 3 


3 4 5 6 6 


63 


7993 


8000 


8007 


8014 


8021 


8028 


8035 


8041 


8048 


8055 1 1 2 3 


3 4 5 5 6 


64 


8062 


8069 


8075 


8082 


8089 


8096 


8102 


8109 


8116 


8122 1 1 2 3 


3 4 5 5 6 


65 


8129 


8136 


8142 


8149 


8156 


8162 


8169 


8176 


8182 


8189 1 1 2 3 


3 4 5 5 6 


66 


8i95 


8202 


8209 


8215 


8222 


8228 


8235 


8241 


8248 


8254 1 1 2 3 


3 4 5 5 6 


67 


8261 


8267 


8274 


8280 


8287 


8293 


8299 


8306 


8312 


8319 1 1 2 3 


3 4 5 5 6 


68 


8325 


833i 


8338 


8344 


835i 


8357 


8363 


8370 


8376 


8382 1 1 2 3 


3 4 4 5 6 


69 


8388 


8395 


8401 


8407 


8414 


8420 


8426 


8432 


8439 


8445 1 1 2 2 


3 4 4 5 6 


70 


8451 


8457 


8463 


8470 


8476 


8482 


8488 


8494 


8500 


8506 1 1 2 2 


3 4 4 5 6 


7i 


8513 


8519 


8525 


8531 


8537 


8543 


8549 


8555 


8561 


8567 1 1 2 2 


3 4 4 5 5 


72 


8573 


8579 


8585 


8591 


8597 


8603 


8609 


8615 


8621 


8627 1 1 2 2 


3 4 4 5 5 


73 


8633 


8639 


8645 


8651 


8657 


8663 


8669 


8675 


8681 


8686 1 1 2 2 


3 4 4 5 5 


74 


8692 


8698 


8704 


8710 


8716 


8722 


8727 


8733 


8739 


8745 1 1 2 2 


3 4 4 5 5 


75 


875i 


8756 


8762 


8768 


8774 


8779 


8785 


8791 


8797 


8802 1 1 2 2 


3 3 4 5 5 


76 


8808 


8814 


8820 


8825 


8831 


8837 


8842 


8848 


8854 


8859 1 1 2 2 


3 3 4 5 5 


77 


8865 


8871 


8876 


8882 


8887 


8893 


8899 


8904 


8910 


8915 1 1 2 2 


3 3 4 4 5 


78 


8921 


8927 


8932 


8938 


8943 


8949 


8954 


8960 


8965 


8971 1 1 2 2 


3 3 4 4 5 


79 


8976 


8982 


8987 


8993 


8998 


9004 


9009 


9015 


9020 


9026 1 1 2 2 


3 3 4 4 5 


80 


9031 


9036 


9042 


9047 


9053 


9058 


9063 


9069 


9074 


9079 1 1 2 2 


3 3 4 4 5 


81 


9085 


9090 


9096 


9101 


9106 


9112 


9117 


9122 


9128 


9133 1 1 2 2 


3 3 4 4 5 


82 


9138 


9143 


9149 


9154 


9159 


9165 


9170 


9175 


9180 


9186 1 1 2 2 


3 3 4 4 5 


83 


9191 


9196 


9201 


9206 


9212 


9217 


9222 


9227 


9232 


9238 1 1 2 2 


3 3 4 4 5 


84 


9243 


9248 


9253 


9258 


9263 


9269 


9274 


9279 


9284 


9289 1 1 2 2 


3 3 4 4 5 


85 


9294 


9299 


9304 


9309 


9315 


9320 


9325 


9330 


9335 


9340 1 1 2 2 


3 3 4 4 5 


86 


9345 


935o 


9355 


9360 


9365 


937o 


9375 


9380 


9385 


9390 1 1 2 2 


3 3 4 4 5 


87 


9395 


9400 


9405 


9410 


9415 


9420 


9425 


9430 


9435 


9440 1 1 2 


2 3 3 4 4 


88 


9445 


945o 


9455 


9460 


9465 


9469 


9474 


9479 


9484 


9489 1 1 2 


2 3 3 4 4 


89 


9494 


9499 


9504 


9509 


9513 


95i8 


9523 


9528 


9533 


9538 1 1 2 


2 3 3 4 4 


90 


9542 


9547 


9552 


9557 


9562 


9566 


957i 


9576 


958i 


9586 1 1 2 


2 3 3 4 4 


9i 


9590 


9595 


9600 


9605 


9609 


9614 


9619 


9624 


9628 


9633 1 1 2 


2 3 3 4 4 


92 


9638 


9643 


9647 


9652 


9657 


9661 


9666 


9671 


9675 


9680 1 1 2 


2 3 3 4 4 


93 


9685 


9689 


9694 


9699 


9703 


9708 


9713 


9717 


9722 


9727 1 1 2 


2 3 3 4- 


94 


973i 


9736 


974i 


9745 


975o 


9754 


9759 


9763 


9768 


9773 1 1 2 


2 3 3 4^! 


95 


9777 


9782 


9786 


9791 


9795 


9800 


9805 


9809 


9814 


9818 1 1 2 


2 3 3 4 4 


96 


9823 


9827 


9832 


9836 


9841 


9845 


9850 


9854 


9859 


9863 1 1 2 


2 3 3 4 4 


97 


9868 


9872 


9877 


9881 


9886 


9890 


9894 


9899 


9903 


9908 1 1 2 


2 3 3 4 4 


98 


9912 


9917 


9921 


9926 


9930 


9934 


9939 


9943 


9948 


9952 1 1 2 


2 3 3 4 4 


99 


9956 


9961 


9965 


9969 


9974 


9978 


9983 


9987 


9991 


9996 1 1 2 


2 3 3 3 4 



26 



AIR, WATER, AND FOOD 



ANTILOGARITHMS 



Loga- 
rithms. 





1 


2 


3 


4 


5 


6 


7 


8 


9 


Proportional parts. 










































1 


2 



3 
I 


4 

1 


5 

1 


6 

1 


7 
2 


8 

2 


9 


O.OO 


1000 


1002 


1005 


1007 


IOO9 


IOI2 


1014 


1016 


1019 


I02I 





2 


O.OI 


1023 


1026 


1028 


IO30 


I033 


I035 


1038 


1040 


1042 


I045 








I 


I 


1 


1 


2 


2 


2 


0.02 


1047 


1050 


1052 


I054 


IO57 


I059 


1062 


1064 


1067 


1069 








I 


I 


1 


1 


2 


2 


2 


O.O3 


1072 


1074 


1076 


1079 


1081 


1084 


1086 


1089 


1091 


IO94 








I 


I 


1 


1 


2 


2 


2 


O.O4 


1096 


1099 


1102 


1 104 


1107 


I IO9 


1112 


1 1 14 


1117 


III9 





I 


I 


I 


1 


2 


2 


2 


2 


O.05 


1122 


1125 


1127 


1130 


1132 


1135 


1138 


1 140 


1 143 


1 146 





I 


I 


I 


1 


2 


2 


2 


2 


O.06 


1 148 


"Si 


ii53 


1156 


1159 


Il6l 


1 164 


1167 


1 169 


II72 





I 


I 


1 


1 


2 


2 


2 


2 


O.07 


"75 


1178 


1 180 


1183 


1186 


H89 


1191 


1 194 


1197 


1 199 





I 


I 


I 


1 


2 


2 


2 


2 


O.08 


1202 


1205 


1208 


I2II 


1213 


I2l6 


1219 


1222 


1225 


1227 





I 


I 


1 


1 


2 


2 


2 


3 


O.O9 


1230 


1233 


1236 


1239 


1242 


1245 


1247 


1250 


1253 


I256 





I 


I 


I 


1 


2 


2 


2 


3 


O.IO 


1259 


1262 


1265 


1268 


1271 


1274 


1276 


1279 


1282 


1285 





I 


I 


I 


1 


2 


2 


2 


3 


O.II 


1288 


1291 


1294 


1297 


1300 


I303 


1306 


1309 


1312 


1315 





I 


I 


I 


2 


2 


2 


2 


3 


O.I2 


1318 


1321 


1324 


1327 


I330 


1334 


1337 


I340 


1343 


1346 





I 


I 


I 


2 


2 


2 


2 


3 


0.13 


1349 


1352 


1355 


1358 


1361 


1365 


1368 


1371 


1374 


1377 


c 


I 


I 


I 


2 


2 


2 


3 


3 


0.14 


1380 


1384 


1387 


I39O 


1393 


I396 


1400 


1403 


1406 


I409 


c 


I 


1 


I 


2 


2 


2 


3 


3 


015 


1413 


1416 


1419 


1422 


1426 


I429 


1432 


1435 


1439 


1442 


c 


I 


I 


1 


2 


2 


2 


3 


3 


0.16 


1445 


1449 


1452 


1455 


1459 


I462 


1466 


1469 


1472 


1476 





I 


I 


I 


2 


2 


2 


3 


3 


0.17 


1479 


1483 


i486 


I489 


1493 


1496 


1500 


I503 


1507 


I5IO 





I 


I 


1 


2 


2 


2 


3 


3 


0.18 


1514 


1517 


1521 


1524 


1528 


1531 


1535 


1538 


1542 


1545 





I 


I 


1 


2 


2 


2 


3 


3 


0.19 


1549 


1552 


1556 


I560 


1563 


1567 


I570 


1574 


1578 


I58l 


c 


I 


I 


I 


2 


2 


3 


3 


3 


0.20 


1585 


1S89 


1592 


1596 


1600 


1603 


1607 


1611 


1614 


l6l8 





I 


I 


1 


2 


2 


3 


3 


3 


0.21 


1622 


1626 


1629 


1633 


1637 


1641 


1644 


1648 


1652 


1656 





I 


I 


2 


2 


2 


3 


3 


3 


0.22 


1660 


1663 


1667 


167I 


1675 


1679 


1683 


1687 


1690 


1694 





I 


I 


2 


2 


2 


3 


3 


3 


0.23 


1698 


1702 


1706 


I7IO 


1714 


1718 


1722 


1726 


1730 


1734 





I 


I 


2 


2 


2 


3 


3 


4 


0.24 


1738 


1742 


1746 


I750 


1754 


1758 


1762 


1766 


1770 


1774 





I 


I 


2 


2 


2 


3 


3 


4 


0.25 


1778 


1782 


1786 


1791 


1795 


1799 


1803 


1807 


1811 


l8l6 





I 


I 


2 


2 


2 


3 


3 


4 


0.26 


1820 


1824 


1828 


1832 


1837 


1841 


1845 


1849 


1854 


1858 





I 


I 


2 


2 


3 


3 


3 


4 


0.27 


1862 


1866 


1871 


1875 


1879 


1884 


1888 


1892 


1897 


I9OI 





I 


I 


2 


2 


3 


3 


3 


4 


0.28 


1905 


1910 


1914 


1919 


1923 


1928 


1932 


1936 


1941 


1945 





I 


I 


2 


2 


3 


3 


4 


4 


0.29 


i95o 


1954 


1959 


I963 


1968 


1972 


1977 


1982 


1986 


1991 





I 


I 


2 


2 


3 


3 


4 


4 


0.30 


1995 


2000 


2004 


2009 


2014 


20l8 


2023 


2028 


2032 


2037 





I 


I 


2 


2 


3 


3 


4 


4 


0.31 


2042 


2046 


2051 


2056 


2061 


2065 


2070 


2075 


2080 


2084 





I 


I 


2 


2 


3 


3 


4 


4 


0.32 


2089 


2094 


2099 


2I04 


2109 


2113 


2118 


2123 


2128 


2133 





I 


I 


2 


2 


3 


3 


4 


4 


033 


2138 


2143 


2148 


2153 


2158 


2163 


2168 


2173 


2178 


2183 





I 


I 


2 


2 


3 


3 


4 


4 


0.34 


2188 


2193 


2198 


2 203 


2208 


2213 


2218 


2223 


2228 


2234 




I 


2 


2 


3 


3 


4 


4 


5 


0.35 


2239 


2244 


2249 


2254 


2259 


2265 


2270 


2275 


2280 


2286 




I 


2 


2 


3 


3 


4 


4 


5 


0.36 


2291 


2296 


2301 


2307 


2312 


2317 


2323 


2328 


2333 


2339 




I 


2 


2 


3 


3 


4 


4 


5 


0.37 


2344 


2350 


2355 


2360 


2366 


2371 


2377 


2382 


2388 


2393 




I 


2 


2 


3 


3 


4 


4 


5 


0.38 


2399 


2404 


2410 


2415 


2421 


2427 


2432 


2438 


2443 


2449 




I 


2 


2 


3 


3 


4 


4 


5 


0.39 


2455 


2460 


2466 


2472 


2477 


2483 


2489 


2495 


2500 


2506 




I 


2 


2 


3 


3 


4 


5 


5 


0.40 


2512 


2518 


2523 


2529 


2535 


2541 


2547 


2553 


2559 


2564 




I 


2 


2 


3 


4 


4 


5 


5 


0.41 


2570 


2576 


2582 


2588 


2594 


260O 


2606 


2612 


2618 


2624 




I 


2 


2 


3 


4 


4 


5 


5 


0.42 


2630 


2636 


2642 


2649 


2655 


2661 


2667 


2673 


2679 


2685 




I 


2 


2 


3 


4 


4 


5 


6 


0.43 


2692 


2698 


2704 


27IO 


2716 


2723 


2729 


2735 


2742 


2748 




I 


2 


3 


3 


4 


4 


5 


6 


0.44 


2754 


2761 


2767 


2773 


2780 


2786 


2793 


2799 


2805 


28l2 




I 


2 


3 


3 


4 


4 


5 


6 


o-45 


2818 


2825 


2831 


2838 


2844 


2851 


2858 


2864 


2871 


2877 




I 


2 


3 


3 


4 


S 


5 


6 


0.46 


2884 


2891 


2897 


2904 


2911 


2917 


2924 


2931 


2938 


2944 




I 


2 


3 


3 


4 


5 


5 


6 


0.47 


2951 


2958 


2965 


2972 


2979 


2985 


2992 


2999 


3006 


30I3 




I 


2 


3 


3 


4 


5 


5 


6 


0.48 


3020 


3027 


3034 


304I 


3048 


3055 


3062 


3069 


3076 


3083 


I 


I 


2 


3 


4 


4 


5 


6 


6 


0.49 


3090 


3097 


3io5 


3112 


3119 


3126 


3133 


3141 


3X48 


3155 


I 


I 


2 


3 


4 


4 


5 


6 6 



APPENDIX A 
ANTILOGARITHMS 



227 



Loga- 






















Proportional parts. 


rithms. 





1 


2 


3 


4 


5 


6 


7 


8 


9 


























1 2 
1 1 


3 

2 


4 
3 


5 

4 


6 
4 


7 

5 


8 

6 


9 


O.50 


3162 


3170 


3177 


3184 


3192 


3199 


3206 


3214 


3221 


3228 


7 


0.5I 


3236 


3243 


3251 


3258 


3266 


3273 


3281 


3289 


3296 


3304 


1 2 


2 


3 


4 


5 


5 


6 


7 


O.52 


33H 


3319 


3327 


3334 


3342 


335o 


3357 


3365 


3373 


338i 


1 2 


2 


3 


4 


5 


5 


6 


7 


0.53 


3338 


3396 


3404 


3412 


3420 


3428 


3436 


3443 


345i 


3459 


1 2 


2 


3 


4 


S 


6 


6 


7 


0.54 


3467 


3475 


3483 


349i 


3499 


35o8 


35i6 


3524 


3532 


3540 


1 2 


2 


3 


4 


5 


6 


6 


7 


o-55 


3548 


3556 


3565 


3573 


358i 


3589 


3597 


3606 


3614 


3622 


1 2 


2 


3 


4 


5 


6 


7 


7 


0.56 


3631 


3639 


3648 


3656 


3664 


3673 


3681 


3690 


3698 


3707 


1 2 


3 


3 


4 


5 


6 


7 


8 


o.57 


3715 


3724 


3733 


374i 


375o 


3758 


3767 


3776 


3784 


3793 


1 2 


3 


3 


4 


5 


6 


7 


8 


0.58 


3802 


3811 


3819 


3828 


3837 


3846 


3855 


3864 


3873 


3882 


1 2 


3 


4 


4 


5 


6 


7 


8 


o.59 


3890 


3899 


3908 


39*7 


3926 


3936 


3945 


3954 


39 6 3 


3972 


1 2 


3 


4 


5 


5 


6 


7 


8 


0.60 


398i 


399o 


3999 


4009 


4018 


4027 


4036 


4046 


4055 


4064 


1 2 


3 


4 


5 


6 


6 


7 


8 


0.61 


4074 


4083 


4093 


4102 


4111 


4121 


4130 


4140 


4150 


4159 


1 2 


3 


4 


5 


6 


7 


8 


9 


0.62 


4169 


4178 


4188 


4198 


4207 


4217 


4227 


4236 


4246 


4256 


1 2 


3 


4 


5 


6 


7 


8 


9 


0.63 


4266 


4276 


4285 


4295 


4305 


4315 


4325 


4335 


4345 


4355 


1 2 


3 


4 


5 


6 


7 


8 


9 


0.64 


4365 


4375 


4385 


4395 


4406 


4416 


4426 


4436 


4446 


4457 


1 2 


3 


4 


5 


6 


7 


8 


9 


0.65 


4467 


4477 


4487 


4498 


4508 


4519 


4529 


4539 


455o 


4560 


1 2 


3 


4 


5 


6 


7 


8 


9 


0.66 


457i 


458i 


4592 


4603 


4613 


4624 


4634 


4645 


4656 


4667 


1 2 


3 


4 


5 


6 


7 


9 


10 


0.67 


4677 


4688 


4699 


4710 


4721 


4732 


4742 


4753 


4764 


4775 


1 2 


3 


4 


5 


7 


8 


9 


10 


0.68 


4786 


4797 


4808 


4819 


4831 


4842 


4853 


4864 


4875 


4887 


1 2 


3 


4 


6 


7 


8 


9 


10 


0.69 


4898 


4909 


4920 


4932 


4943 


4955 


4966 


4977 


4989 


5000 


1 2 


3 


5 


6 


7 


8 


9 


10 


0.70 


5012 


5023 


5035 


5047 


5058 


5070 


5082 


5093 


5105 


5ii7 


1 2 


4 


5 


6 


7 


8 


9 


II 


0.71 


5129 


5140 


5152 


5164 


5176 


5188 


5200 


5212 


5224 


5236 


1 2 


4 


5 


6 


7 


8 


10 


II 


0.72 


5248 


5260 


5272 


5284 


5297 


5309 


532i 


5333 


5346 


5358 


1 2 


4 


5 


6 


7 


9 


10 


11 


o.73 


5370 


5383 


5395 


5408 


5420 


5433 


5445 


5458 


547o 


5483 


1 3 


4 


5 


6 


8 


9 


10 


11 


0.74 


5495 


55o8 


552i 


5534 


5546 


5559 


5572 


5585 


5598 


5610 


1 3 


4 


5 


6 


8 


9 


10 


12 


o.75 


5623 


5636 


5649 


5662 


5675 


5689 


5702 


5715 


5728 


574i 


I 3 


4 


5 


7 


8 


9 


10 


12 


0.76 


5754 


5768 


578i 


5794 


5808 


5821 


5834 


5848 


5861 


5875 


I 3 


4 


5 


7 


8 


9 


11 


12 


0.77 


5888 


5902 5916 


5929 


5943 


5957 


597o 


5984 


5998 


6012 


1 3 


4 


5 


7 


8 


10 


11 


12 


0.78 


6026 


6039 


6053 


6067 


6081 


6095 


6109 


6124 


6138 


6152 


I 3 


4 


6 


7 


8 


IC 


11 


13 


0.79 


6166 


6180 


6194 


6209 


6223 


6237 


6252 


6266 


6281 


6295 


I 3 


4 


6 


7 


9 


10 


11 


13 


0.80 


6310 


6324 


6339 


6353 


6368 


6383 


6397 


6412 


6427 


6442 


I 3 


4 


6 


7 


9 


10 


12 


13 


0.81 


6457 


6471 


6486 


6501 


6516 


6531 


6546 


6561 


6577 


6592 


2 3 


5 


6 


8 


9 


11 


12 


14 


0.82 


6607 


6622 


6637 


6653 


6668 


6683 


6699 


6714 


6730 


6745 


2 3 


5 


6 


8 


9 


11 


12 


14 


0.83 


6761 


6776 


6792 


6808 


6823 


6839 


6855 


6871 


6887 


6902 


2 3 


5 


6 


8 


9 


11 


13 


14 


0.84 


6918 


6934 


6950 


6966 


6982 


6998 


7015 


7031 


7047 


7063 


2 3 


5 





8 


10 


11 


13 


IS 


0.85 


7079 


7096 


7112 


7129 


7145 


7161 


7178 


7194 


7211 


7228 


2 3 


5 


7 


8 


10 


12 


13 


15 


0.86 


7244 


7261 


7278 


7295 


73" 


7328 


7345 


7362 


7379 


7396 


2 3 


5 


7 


8 


10 


12 


13 


15 


0.87 


7413 


743° 


7447 


7464 


7482 


7499 


75i6 


7534 


755i 


7568 


2 3 


5 


7 


9 


10 


12 


14 


16 


0.88 


7586 


7603 


7621 


7638 


7656 


7674 


7691 


7709 


7727 


7745 


2 4 


5 


7 


9 


11 


12 


14 


16 


0.89 


7762 


7780 


7798 


7816 


7834 


7852 


7870 


7889 


7907 


7925 


2 4 


5 


7 


9 


11 


13 


14 


16 


0.90 


7943 


7962 


798o 


7998 8017 


8035 


8054 


8072 


8091 


8110 


2 4 


« 


7 


9 


11 


13 


15 


17 


0.91 


8128 


8147 


8166 


81858204 


8222 


8241 


8260 


8279 


8299 


2 4 


6 


8 


9 


11 


13 


15 


17 


0.92 


8318 


8337 


8356 


8375^395 


8414 


8433 


8453 


8472 


8492 


2 4 


6 


8 


10 


12 


14 


15 


17 


°-93 


8511 


8531 


855i 


85708590 


8610 


8630 


8650 


8670 


8690 


2 4 


6 


8 


10 


12 


14 


16 


18 


0.94 


8710 


8730 


8750 


8770:8790 


8810 


8831 


8851 


8872 


8892 


2 4 


6 


8 


10 


12 


14 


16 


18 


°-95 


8913 


8933 


8954 


89748995 


9016 


9036 


9057 


9078 


9099 


2 4 


^ 


8 


10 


12 


15 


17 


19 


0.96 


9120 


9141 


9162 


9183 9204 


9226 


9247 


9268 


92909311 


2 4 


6 


8 


11 


13 


15 


17 


19 


0.97 


9333 


9354 


9376 


93979419 


9441 


9462 


9484 


9506 9528 


2 4 


7 


9 


11 


13 


15 


17 


20 


0.98 


9550 9572 


9594 


9616 9638 


9661 


9683 


9705 


9727 


975o 


2 4 


7 


9 


11 


13 


16 


18 


20 


0.99 


97729795 


9817 


9840 9863 


9886 9908 


9931 


9954 


9977 


2 5 


7 


9 


11 


14 


16 


18 


20 



APPENDIX B 

REAGENTS 

Air Analysis 

Pettenkofer Method. — Barium Hydroxide. — A solution con- 
taining about 4 grams of BaO and 0.2 gram of BaCl 2 to the liter. 
(1 c.c. = 1 mg. C0 2 , approximately.): 

Sulphuric Acid. — Dilute 45.45 c.c. of normal sulphuric acid 
to one liter. (1 c.c. = 1 mg. CO2.) To standardize the solu- 
tion measure 25 c.c. into a weighed platinum dish, add dilute 
ammonia-water in slight excess, evaporate to dryness on the 
water-bath, and dry at 120 C. to constant weight. 

Standard Lime-water. — (For Popular Tests.) — Shake one 
part of freshly slaked lime with 20 parts of distilled water for 
twenty minutes and let the solution stand overnight or until 
perfectly clear. This solution should be very nearly equiva- 
lent to the above standard sulphuric acid. To a liter of 
distilled water add 2.5 c.c. of a solution of 0.7 gram of phenol- 
phthalein in 100 c.c. of 50 per cent alcohol and add lime-water 
drop by drop until a slight permanent pink color is produced. 
Then add 6.3 c.c. of the above calcium hydroxide solution. The 
resulting solution is the standard lime-water used for the tests. 

Water Analysis 

For Ammonia. — Water Free from Ammonia. — The ammonia- 
free water used in this laboratory is made by redistilling distilled 
water from a solution of alkaline permanganate in a steam-heated 
copper still. Only the middle portion of the distillate is collected. 
Oftentimes the distillate from a good spring- water may be used. 

Nessler's Reagent. — Dissolve 61.750 grams KI in 250 c.c. 
distilled water and add a cold solution of HgCl 2 which has been 
saturated by boiling with an excess of the salt and allowing it 

228 



APPEXDIX 229 

to crystallize out. Add the HgCl 2 cautiously until a slight per- 
manent red precipitate (HgL) appears. Dissolve this slight 
precipitate by adding 0.750 gram powdered KI. Then add 
150 grams of KOH dissolved in 250 c.c. of water. Make up to 
a liter and allow it to stand over night to settle. This solution 
should give the required color with ammonia within five minutes, 
and should not precipitate within two hours. 

Alkaline Permanganate. — Dissolve 233 grams of the best 
stick potash in 350 c.c. of distilled water. Filter this strong 
solution, if necessary, through a layer of glass wool on a por- 
celain filter-plate. Dilute with 700 to 750 c.c. of distilled water 
to a specific gravity of 1.125, a dd 8 grams of potassium per- 
manganate crystals, and boil down to one liter to free the solution 
from nitrogen. Each new lot of reagent must be tested before 
being used, but when the chemicals used are all good there 
should be no correction needed for ammonia in the solution. 

Standard Ammonia Solution. — Dissolve 3.82 grams chemi- 
cally pure XH4CI in a liter of water free from ammonia. This 
is the strong solution from which the standard solution is 
made by diluting 10 c.c. to a liter with water free from am- 
monia. One cubic centimeter of the standard solution = 
0.00001 gram nitrogen. This solution, like the nitrite standard 
and other dilute solutions, must be preserved in sterilized bot- 
tles protected from dust and organic matter. 

For Nitrites. — Standard Nitrite Solution. — The pure silver 
nitrite used in making this solution is prepared by the double 
decomposition of silver nitrate and potassium nitrite, and re- 
peated crystallizations from water of the rather difficultly solu- 
ble silver nitrite. 1.1 grams of this silver nitrite are dissolved 
in nitrite-free water, the silver completely precipitated by the 
addition of the standard salt solution used in the determination 
of chlorine, and the solution made up to 1 liter. 100 c.c. of this 
strong solution are diluted to 1 liter, and 10 c.c. of this last 
solution again diluted to 1 liter. The final solution is the one 
used in preparing standards. 1 c.c. = 0.0000001 gram nitrogen. 

Sulphanilic Acid. — Dissolve 3.3 grams sulphanilic acid in 



23O APPENDIX 

750 c.c. of water by the aid of heat, and add 250 c.c. glacial 
acetic acid. 

N aphthylamine Acetate. — Boil 0.5 gram of a-naphthylamine 
in 100 c.c. of water in a small Erlenmeyer flask for about five 
minutes, filter through a plug of washed absorbent cotton, add 
250 c.c. glacial acetic acid, and dilute to 1 liter. 

For Nitrates. — Standard Nitrate Solution. — Dissolve 0.720 
gram of pure recrystallized KN0 3 in 1 liter of water. Evapo- 
rate 10 c.c. of this strong solution cautiously on the water-bath, 
moisten quickly and thoroughly with 2 c.c. of phenol-disul- 
phonic acid, and dilute to 1 liter for the standard solution. 
1 c.c. = 0.000001 gram nitrogen. 

Phenol-disulphonic Acid. — Heat together 3 grams synthetic 
phenol with 37 grams pure, concentrated H 2 S0 4 in a boiling 
water-bath for six hours. 

Potassium Hydroxide. — 30 per cent. 

For Kjeldahl Process. — Sulphuric Acid. — Sp. gr. 1.84. 
This should be free from nitrogen. May be obtained from 
Baker and Adamson, Easton, Pa. 

Potassium Hydroxide. — Dissolve 350 grams of the best stick 
potash in 2.25 liters of water and boil down to something less 
than a liter with 3 grams of permanganate crystals. When 
cold, dilute to a liter with water free from ammonia. 

For Chlorine. — Salt Solution. — Dissolve 16.48 grams of 
fused NaCl in a liter of distilled water. For the standard 
solution dilute 100 c.c. of this strong solution to 1 liter. 1 c.c. = 
0.001 gram chlorine. 

Silver Nitrate. — Dissolve about 2.42 grams of AgN0 3 (dry 
crystals) in 1 liter of chlorine-free water. 1 c.c. = 0.0005 gram 
CI, approximately. Standardize against the NaCl solution. 

Potassium Chromate. — Dissolve 50 grams neutral K 2 Cr0 4 in 
a little distilled water. Add enough AgN0 3 to produce a slight 
red precipitate. Filter and make the filtrate up to a liter with 
water free from chlorine. 

Milk of Alumina for Decolorization. — Dissolve 125 grams of 
potash or ammonia alum in a liter of distilled water. Pre- 



APPENDIX 231 

cipitate the A1(0H) 3 by the cautious addition of NH 4 OH. 
Wash the precipitate in a large jar by decantation until free from 
chlorine, nitrites, and ammonia. 

For Hardness. — Standard Calcium Chloride Solution. — Dis- 
solve 0.200 gram of pure Iceland spar in dilute HC1, taking care 
to avoid loss by spattering, and evaporate to dryness several 
times, to remove the excess of acid. Dissolve the calcium 
chloride thus formed in 1 liter of water. 

Standard Soap Solution. — Dissolve 100 grams of the best 
white, dry castile soap in a liter of 80 per cent alcohol. Of this 
strong solution dissolve 75 to 100 c.c. in a liter of 70 per cent 
alcohol. This solution must have 70 per cent alcohol added to 
it until 14.25 c.c. of it give the required lather with 50 c.c. of 
the above CaCl 2 solution. 

Erythrosine Indicator. — Dissolve 0.1 gram of erythrosine in 
1 liter of water. 

Methyl Orange Indicator. — Dissolve 0.1 gram Aniline Orange, 
Merck, (Methyl) or Orange III in a few cubic centimeters of 
alcohol and dilute to 100 c.c. with distilled water. 

Soda Reagent. — Equal parts of sodium hydroxide and sodium 

N 
carbonate solutions, the mixture to be approximately — 

10 

For Iron. — Standard Solution. — Dissolve 0.7 gram of crys- 
tallized ferrous ammonium sulphate in 50 c.c. of distilled water 
and add 20 c.c. of dilute sulphuric acid. Warm the solution 
slightly and add potassium permanganate until the iron is com- 
pletely oxidized. Dilute the solution to one liter. One cubic 
centimeter of the standard solution equals 0.1 mg. Fe. 

Potassium Sulphocyanate. — 20 grams per liter. 

Hydrochloric Acid. — One part HC1 (sp. gr. 1.20) to 1 part of 
water. 

Potassium Permanganate. — Five grams KMn0 4 in 1 liter of 
water. 

For Dissolved Oxygen. — Manganous Sulphate. — 48 grams 
of MnS0 4 . 4 H 2 in 100 c.c. of water. 

Alkaline Potassium Iodide. — 360 grams of NaOH and 100 
grams of KI in 1 liter of water. 



232 APPENDIX 

Hydrochloric Acid. — Sp. gr. 1.20. 

Potassium Acetate. — 100 grams in 100 c.c. of water. 

N 

Sodium Thiosulphate Solution. • Dissolve 2.48 grams of 

100 

the pure crystallized salt in water and dilute to one liter. Stand- 

N 
ardize against a — potassium bichromate solution. 
100 

For Oxygen Consumed. — Standard Ammonium Oxalate Solu- 
tion. — Dissolve 0.888 gram pure ammonium oxalate in 1 liter 
of distilled water. One cubic centimeter is equivalent to 0.0001 
gram oxygen consumed. 

Potassium Permanganate Solution. — Dissolve 0.4 gram potas- 
sium permanganate in 1 liter of distilled water and standardize 
against the ammonium oxalate solution according to the method 
described in the text. 

N 
For Free Carbonic Acid. — Standard — Sodium Carbonate 

22 

Solution. 

For Lead. — Standard Lead Solution. — To a strong solution of 
lead acetate add a slight excess of H2SO4, filter off and wash the 
precipitate. Dissolve it in ammonium acetate solution, made 
by neutralizing glacial acetic acid with strong ammonia. Make 
up to a known volume and determine the lead in an aliquot 
part by precipitating with K 2 Cr 2 07 and weighing the lead chro- 
mate. Dilute an aliquot part to make a convenient standard, 
say about 1 c.c. = 0.001 gram of Pb. 

Food Analysis 

Pumice. — Bits of ignited pumice, about the size of a pea, 
dropped while hot into water and bottled for use. 

Alcohol (for Reichert-Meissl method). — 95 per cent alcohol 
redistilled from potassium hydroxide. 

Iodine Solution (for Hanus' method) . — This is conveniently 
made up according to the directions of Hunt.* Dissolve 13.2 
grams iodine in 1 liter of glacial acetic acid (99 per cent, show- 

* /. Soc. Chem. Ind., 21, IQ02, 454. 



APPENDIX 233 

ing no reduction with bichromate and sulphuric acid). This will 
best be done by adding the acetic acid in portions and heating 
on the water-bath with frequent shaking. To the cold solution 
add enough bromine to double the halogen content, as shown 
by titration. Three cubic centimeters of bromine is sufficient. 
A slight excess of iodine is not detrimental. 

Anhydrous Ether. — Wash ordinary ether several times with 
distilled water and add solid caustic potash until most of the 
water has been removed. Then add small pieces of clean 
metallic sodium until there is no further evolution of hydrogen 
gas. The ether thus prepared should be kept over metallic 
sodium and a tube of calcium chloride should be inserted in the 
stopper, in order to allow the escape of any accumulated gas. 

Potassium Sulphide. — Dissolve 40 grams of the crystallized 
salt in 1 liter of water and filter through glass wool. 

Potassium Hydroxide (for Kjeldahl process). — Dissolve 700 
grams of the best quality of stick potash in water and dilute to 
1 liter. 

Basic Lead Acetate. — Boil for half an hour 440 grams of lead 
acetate and 264 grams of litharge in 1500 c.c. of water. Cool 
and dilute to 2 liters. Allow to settle and siphon off the clear 
liquid. (Specific gravity about 1.27, containing about 35 per 
cent of the basic salt.) 

Ferric Alum. — Dissolve 2 grams of ferric alum in 100 c.c. of 
water, boil the solution until a precipitate appears, and filter. 

Fehling , s Solution. — (a) Dissolve 69.28 grams of C.P. crys- 
tallized copper sulphate, carefully dried between blotting-paper, 
in water and make up to 1 liter, including 1 c.c. of strong sul- 
phuric acid: (b) Dissolve 346 grams of sodium potassium tar- 
trate and 100 grams of sodium hydroxide in water and make 
up to a liter. 






BIBLIOGRAPHY 

AIR 

The following list contains the more important books and 
articles of recent publication. 

Barker, A. H. The Theory and Practice of Heating and Ventilation. The 
Carton Press, London, 191 2.. 

Greene, A. M. The Elements of Heating and Ventilation. John Wiley & Sons, 
New York, 1913. 

Hammarsten-Mandel. A Text Book of Physiological Chemistry. John 
Wiley & Sons, New York, 1908. 

Hoffman, J. D. Handbook for Heating and Ventilating Engineers. McGraw- 
Hill Book Co., New York, 19 13. 

Macfie, Ronald C. Air and Health. Methuen & Co., London, 1909. 

Richards, Ellen H. Conservation by Sanitation. John Wiley & Sons, New 
York, 191 1. 

Rosenau, M. J. Preventive Medicine and Hygiene. Appleton, New York, 

1913. 

Shaw, W. W. Air Currents and the Laws of Ventilation. University Press, 
Cambridge, Eng., 1907. 

Soper, J. A. Air and Ventilation in Subways. John Wiley & Sons, New 
York, 1908. 

Talbot, Marion. House Sanitation. Whitcomb & Barrows, Boston, 1913. 

Standard Methods for the Examination of Air. American Public Health Asso- 
ciation, Boston, 1910. 

Affleck. Ventilation of Gymnasia. Am. Phys. Ed. Rev., 1912. 

Air Supply and Ventilation Number. Am. J. Pub. Health, Nov., 1913, 3, 
pp. 1123-1210. 

Crowder. A Study of the Ventilation of Sleeping Cars. Arch. Intern. Med., 
1911, 7, pp. 85-133. 

Jordan and Carlson. Ozone: Its Bactericidal, Physiologic and Deodorizing 
Action. J. Am. Med. Assn., 1913, 61, p. 1007. 

McCurdy. Recirculated Air. Am. Phys. Ed. Rev., 1913, Dec. 

Norton. Ventilation of Sleeping Cars. Science Conspectus, 191 2, 2, pp. 
79-82. 

Transactions of the 15th International Congress of Hygiene and Demography. 
1913, Vol. 2, Pt. II. 

Ventilation Symposium. J. Ind. Eng. Chem., 1914, 6, p. 245. 

Vosmaer. Industrial Uses of Ozone. J. Ind. Eng. Chem., 1914, 6, p. 229. 

Winslow & Kligler. A Quantitative Study of Bacteria in City Dust. Am. 
J. Pub. Health, 191 2, 2, p. 663. 

234 



BIBLIOGRAPHY 235 

WATER 

The following list contains the most important recent books 
on water, from a sanitary standpoint. 

Don, J. & Chlsholm, J. Modem Methods of Water Purification. 2nd Ed., 
Longmans, Green & Co., New York, 1913. 

Fuller, M. L. Domestic Water Supplies for the Farm. John Wiley & Sons, 
New York, 191 2. 

Gerhard, W. P. The Sanitation, Water Supply and Sewage Disposal of 
Country Houses. D. Van Nostrand Co., New York, 1909. 

Hazen, Allen. The Filtration of Public Water Supplies. . 3rd Ed., John 
Wiley & Sons, New York, 19 10. 

Hazen, Allen. Clean Water and How to Get It. 2nd Ed., John Wiley & 
Sons, New York, 19 14. 

Mason, W. P. Examination of Water. 4th Ed., John Wiley & Sons, New- 
York, 191 2. 

Mason, W. P. Water Supply. John Wiley & Sons, New York, 1909. 

Prescott, S. C. and Winslow, C. E. A. Elements of Water Bacteriology. 
3rd Ed., John Wiley & Sons, New York, 1913. 

Rideal, S. Water and Its Purification. Lockwood & Son, London, 1902. 

Stocks, H. B. Water Analysis. Griffin & Co., London, 191 2. 

Thresh, J. C. The Examination of Waters and Water Supplies. 2nd Ed., P. 
Blackiston's Son & Co., Philadelphia, 1913. 

Thresh, J. C. A Simple Method of Water Analysis. 7th Ed., Churchill, 
London, 191 2. 

Tillsman, J. Translation by H. S. Taylor. Water Purification and Sewage 
Disposal. D. Van Nostrand Co., New York, 1913. 

Whipple, G. C. The Microscopy of Drinking Water. 3rd Ed., John Wiley 
& Sons, New York, 19 14. 

Whipple, G. C. The Value of Pure Water. John Wiley & Sons, New York, 
1907. 

Annual Reports, Massachusetts State Board of Health, 1879 to 1912. 

Reports of the Metropolitan Water Board, New York City. 

Reports of the Royal Commission on Sewage Disposal, England. 

FOOD 

Only the general books and bulletins published since 1890 
which are most available to the student are given here. A de- 
tailed list of all important references to food will be found at 
the end of each chapter in Leach's Food Inspection and Analysis. 

Allen, A. H. Commercial Organic Analysis. 4th Ed., Blakiston, Phila., 
1911. 

Bailey, E. H. S. Sanitary and Applied Chemistry. Macmillan, New York, 
1906. 



236 BIBLIOGRAPHY 

Blyth, A. W. and M. W. Foods, their Composition and Analysis. Griffin, 
London, 1909. 

Farrington, E. H., and Woll, F. W. Testing Milk and Its Products. Men- 
dota Book Co., Madison, Wis., 1908. 

Girard, C. and Dupre, A. Analyse des Matieres Alimentaires. 2d Ed., 
Dunod, Paris, 1904. 

Hutchison, R. Food and Dietetics. William Wood, New York, 1908. 

Konig, J. Die Menschlichen Nahrungs = u. Genussmittel. Springer, Berlin, 
1904. 

. Die Untersuchung landwirtschaftlich und gewerblich wichtiger Stoffe. 

Parey, Berlin, 191 1. 

Leach, A. E. Food Inspection and Analysis. Wiley, New York, 1909. 

Leffmann, H. and Beam, W. Food Analysis. Blakiston, Phila., 1905. 

Lewkowitsch, J. Oils, Fats and Waxes. Macmillan, New York, 1909. 

Mitchell, C. A. Flesh Foods. Griffin, London, 1900. 

Moor, C. G. Standards for Food and Drugs. Bailliere, Tindall & Cox, London, 
1902. 

Norton, A. P. Food and Dietetics. School of Home Economics, Chicago, 
1907. 

Olsen, J. C. Pure Food. Ginn & Co., Boston, 191 1. 

Pearmain, T. H., and Moor, C. G. The Analysis of Food and Drugs. Bailliere, 
Tindall & Cox, London, 1897. 

Richards, E. H. The Cost of Food. Wiley, New York, 1901. 

. Food Materials and their Adulterations. Home Science Pub. Co., 

Boston, 1908. 

Richmond, H. D. Dairy Chemistry. London, 1889. 

Rupp, G. Die Untersuchung von Nahrungsmitteln. Winter, Heidelberg, 1900. 

Sherman, H. C. Chemistry of Food and Nutrition. Macmillan, New York, 
1911. 

. Organic Analysis. Macmillan, New York, 191 2. 

Snyder, H. Human Foods. Macmillan, New York, 1908. 

Van Slyke, L. L. Testing Milk and Milk Products. Orange Judd, New York, 
1911. 

Wiley, H. W. Principles and Practice of Agricultural Analysis. Vol. III. 
Chem. Pub. Co., Easton, Pa., 1897. 

. Foods and their Adulteration. Blakiston, Phila., 1911. 

The following bulletins of the United States Department of 
Agriculture will also be found useful for study or reference on 
the general question of food: 

Office of Experiment Stations, Bulletins 

No. 9. Fermentations of Milk. 1892. 

11. Analyses of American Feeding Stuffs. 1892. 

21. Chemistry and Economy of Food. 1895. 

25. Dairy Bacteriology. 1895. 



INDEX 245 

Page 

Malted cereals, analysis of 189 

Manganese sulphate solution 231 

Marsh test for caramel 204 

Methyl orange indicator 231 

Milk, composition of 136 

detection of added water 158 

interpretation of analysis 156 

serum, examination of ! 149 

solids, calculation of 148 

sugar, determination of 145 

variations in compositions of 137 

Mills-Reincke phenomenon 45 

Mineral matter in water 65 

determination of 87 

salts, value in food 116 

Misbranding 125 

Moisture in cereals 180 

see Humidity. 

Motion of air, determination of 22 

effect on heat loss 14 

Naphthylamine acetate solution 80, 230 

Nessler reagent , 72, 228 

Nitrate solution, standard 230 

Nitrates in water, determination of 82 

significance of 63 

Nitrite solution, standard 229 

Nitrites in air, determination of 42 

in water, determination of 80 

significance of 63 

Nitrogen cycle 60 

in water, determination of total 78 

Nitrogen-free extract 184 

Nitrogenous substances, function of 113 

Nutritive ratio 117 

Odor in water, determination of 106 

Odors in water, extermination of 48 

Oleomargarine 163 

Organic matter in water 66 

determination of 85 

Oxygen consumed, determination of 85 

dissolved in water, determination of 100 

significance of 66 

in expired air , n 

in inspired air 9 

table of saturation of water with 103 



246 INDEX 

Page 

Ozone, use in purifying air 20 

sterilizing water 54 

Pettenkofer method for carbon dioxide 33 

Pettersen-Palmquist apparatus 27 

Phenoldisulphonic acid reagent 82, 230 

Pollution in wells, methods of tracing 50 

past 63 

Potassium acetate solution 232 

chromate indicator 230 

iodide solution, alkaline 231 

permanganate, alkaline 73, 229 

permanganate solution, standard 232 

sulphocyanate reagent 89, 231 

Preservatives, detection in butter 166 

Preservatives in food 132 

Protein by Kjeldahl method 182 

Proteins in milk 146 

Psychrometer 22 

Putrescibility test 104 

Radiator, platinum 88 

Rain fall, average 46 

water 45 

Rapid methods for air analysis 35 

Reagents for air analysis 228 

water analysis 228 

Reducing sugar, Munson and Walker's table 221 

Refractive index 173 

Refractometer 174 

principle of 175 

Reichert-Meissl number 167 

Renovated butter, manufacture of 163 

Residue on evaporation, determination of 87 

Resins, in vanilla 203 

Respiration n 

Salicylic acid, detection of 196 

Salt, determination in butter 166 

Sanitary science, importance of 2 

Sanitation, scope of chemistry of 1 

Sediment, determination of 108 

Self-purification of streams 47 

Septic tank 61 

Sewage analysis 67, 109 

purification required 44 

tables of analyses of 213 



BIBLIOGRAPHY 237 

28. (Rev. Ed.) Chemical Composition of American Food Materials. 1895. 

29. Dietary Studies at the University of Tennessee. 1896. 

31. Dietary Studies at the University of Missouri. 1896. 

32. Dietary Studies at Purdue University. 1896. 

34. Carbohydrates of Wheat, Maize, Flour, and Bread. 1896. 

35. Food and Nutrition Investigations in New Jersey. 1896. 

37. Dietary Studies at the Maine State College. 1897. 

38. Dietary Studies — Food of the Negro in Alabama. 1897. 
40. Dietary Studies in New Mexico. 1897. 

43. Composition and Digestibility of Potatoes and Eggs. 1897. 

44. Metabolism of Nitrogen and Carbon in the Human Organism. 1897. 

45. A Digest of Metabolism Experiments. 1897. 

46. Dietary Studies in New York City. 1898. 

52. Nutrition Investigations in Pittsburgh, Pa. 1898. 

53. Nutrition Investigations at the University of Tennessee. 1898. 

54. Nutrition Investigations in New Mexico. 1898. 

55. Dietary Studies in Chicago. 1898. 

63. Experiments on the Conservation of Energy in the Human Body. 
1899. 

66. Creatin and Creatinin. 1899. 

67. Bread and Bread Making. 1899. 

69. Experiments on the Metabolism of Matter and Energy in the Human 

Body. 1899. 

71. Dietary Studies of Negroes. 1899. 

75. Dietary Studies of University Boat Crews. 1900. 

84. Nutrition Investigations at the California Agr. Expt. Station. 1900. 

85. Investigations on the Digestibility and Nutritive Value of Bread. 1900. 
89. Effect of Muscular Work on Digestion of Food and Metabolism of 

Nitrogen. 1901. 
91. Nutrition Investigations at the University of Illinois, etc. 1901. 
98. Effect of Severe and Prolonged Muscular Work on Food Consumption 

Digestibility, and Metabolism. 1901. 

101. Studies on Bread and Bread Making. 1901. 

102. Losses in Cooking Meat. 1901. 

107. Nutrition Investigations among Fruitarians and Chinese. 1901. 

109. Metabolism of Matter and Energy in the Human Body. 1902. 

116. Dietary Studies in New York City. 1902. 

117. Effect of Muscular Work upon Digestibility of Food and Metabolism 

of Nitrogen. 1902. 
121. Metabolism of Nitrogen, Sulphur, and Phosphorus in the Human 

Organism. 1902. 
126. Digestibility and Nutritive Value of Bread. 1903. 
129. Dietary Studies: Boston and other Places. 1903. 
132. Further Investigations among Fruitarians. 1903. 
152. Dietary Studies with Harvard University Students. 
162. Studies on Influence of Cooking on Nutritive Value of Meats. 
227. Calcium, Magnesium and Phosphorus in Food and Nutrition. 



238 BIBLIOGRAPHY 

Bureau of Chemistry, Bulletins 

No. 13. Foods and Food Adulteration — (Ten Parts). 

45. Analyses of Cereals. 

50. Composition of Maize. 

59. Composition of American Wines. 

61. Pure Food Laws of Foreign Countries. 

66. Fruits and Fruit Products. 

69. Foods and Food Control. 

72. American Wines at Paris Exposition of 1900. 

77. Olive Oil and Its Substitutes. 

84. Influence of Food Preservatives and Artificial Colors on Digestion and 

Health. 

100. Some Forms of Food Adulteration and Simple Methods for their De- 
tection. 

107. Official and Provisional Methods of Analysis. 

no. Chemical Analysis and Composition of American Honeys. 

114. Meat Extracts and Similar Preparations. 

115. Effects of Cold Storage on Eggs, Quail and Chickens. 

120. Feeding Value of Cereals. 

122. Annual Proceedings A. O. A. C. 

132. Annual Proceedings A. O. A. C. 

137. Annual Proceedings A. O. A. C. 

152. Annual Proceedings A. O. A. C. 

162. Annual Proceedings A. O. A. C. 

164. Graham Flour. 

Farmers' Bulletins 

No. 23. Foods: Nutritive Value and Cost. 1894. 
29. Souring of Milk. 1895. 
34. Meats: Composition and Cooking. 1896. 
74. Milk as Food. 1898. 

85. Fish as Food. 1898. 
93. Sugar as Food. 1899. 

112. Bread and the Principles of Bread Making. 1900. 

121. Beans, Peas, and other Legumes as Food. 1900. 
128. Eggs and their Uses as Food. 1901. 

131. Household Tests for Detection of Oleomargarine and Renovated Butter. 

1901. 

142. The Nutritive and Economic Value of Food. 1901. 

182. Poultry as Food. 

249. Cereal Breakfast Foods. 

252. Maple Sugar and Sirup. 

293. Use of Fruit as Food. 

332. Nuts and their Uses as Food. 

363. Use of Milk as Food. 

490. Bacteria in Milk. 



BIBLIOGRAPHY 239 

Much valuable information will also be found in the regular bulletins and re- 
ports of several of the State experiment stations and boards of health, notably 
those of Connecticut, North Dakota, Maine, Kansas, New Hampshire, Vermont 
and Massachusetts. The "Food Inspection Divisions" and "Notices of Judg- 
ment" issued from time to time in the enforcement of the Federal Pure Food 
Law also contain interesting information concerning the adulteration of food. 



INDEX 



Page 

Acid, sulphanilic, reagent 229 

sulphuric, reagent for air analysis 228 

Adams' method for fat 141 

Adulteration, cause of 124 

character of 128 

definition of 124 

extent of 128 

Air, amount of, required 18 

bacteria in " 10, 42 

collection of samples of 24 

composition of expired n 

composition of inspired 9 

dust in 9 

essential to life 2 

humidity of 9, 14 

methods of analysis of 21 

purification 20 

poisonous gases in 10 

Alcohol, determination of 191 

table 217 

Alkalinity, determination of, in water 92 

Alum, determination of, in water 95 

Alumina, milk of 230 

Ammonia, albuminoid, determination of 72 

significance of 61 

free, determination of 72 

significance of 62 

free water 228 

standard solution of 229 

Ammonium oxalate solution, standard 232 

Analysis, air, methods of 21 

water, methods of 69 

accuracy of methods of 59 

expression of results of 58 

interpretation of results of 56 

Ash, in cereals 180 

in wine 193 

of milk 141 

241 



242 INDEX 

Page 

Babcock method for fat 142 

Bacteria in air, 10 

determination of 42 

Barometers 21 

Basic lead acetate 233 

Beer, analysis of 197 

Benzoic acid, detection of 196 

Bibliography 234 

Bleach, use of, in water sterilization 54 

Boric acid, detection in milk 154 

Breakfast foods 130 

Butter, analysis of 165 

composition of 162 

Federal standard for 164 

microscopic examination 178 

Butter-fat, composition of 163 

Calcium chloride solution, standard 231 

Calorie, definition of 117 

Calorific value 117 

Cane-sugar, detection in milk 150 

Caramel in vanilla extracts 204 

Carbohydrates, function of 115 

Carbon dioxide, allowable amounts in air 17 

determination of, in air 27 

in water 84 

in expired air n 

in inspired air 9 

poisonous action of 12 

table of weights of cubic centimeters of 209 

use as a ventilation test 17 

Carbon monoxide in air 10 

determination of 40 

Carbonaceous matter in water, determination of 85 

Casein, determination in milk 146 

Cereals, analysis of 180 

composition of 181 

Chloride of lime, use in water sterilization 54 

Chlorides in water, significance of 64 

determination of 84 

Chlorine, map of normal 65 

in water, see chlorides. 

Cholera 44 

Coal-tar dyes, detection of 194 

Cohen and Appleyard method for air analysis 37 

Collection of samples of air 24 

water 69 



INDEX 243 

Page 

Color in water, determination of 105 

Color, detection in milk 154 

Colors in food 132 

Comfort 11 

curve of 16 

Cooking, changes caused by 116 

Coumarin, determination of 201 

Crowd poisoning, theory of 12 

Crude fibre 188 

Dextrin, determination in cereals 185 

Dietaries 120 

Dust in air 9 

determination of 23 

Electric muffle furnace 88 

Erythrosine indicator 231 

Ether, anhydrous 233 

extract in cereals 182 

Extract in beer-wort 222 

in wine 192 

in wine, table 220 

Fat, determination in milk 141 

in cereals 182 

Fats, function of 114 

Fehlings' solution 233 

Ferric alum 233 

Ferrous ammonium sulphate, standard solution 89, 231 

Filter galleries 50 

Filters, water 52 

Filtration, methods of 52 

Fitz shaker 39 

Food, composition of 112 

definition and uses 111 

essential for lif e 5 

materials, composition of 118 

principles 112 

values, discussion of 122 

Foods, predigested 129 

"Fore" milk 138 

Formaldehyde, detection in milk 151 

Free acids, in wine 193 

Gottlieb method for fat 143 

Ground waters 48 

Gunning method 184 



244 INDEX 

Page 

Hale and Melia method for dissolved oxygen 101 

Hanus method 171 

Hardness, acid method for 91 

permanent, determination of s . 93 

soap method for 90 

table of 216 

temporary, determination of 92 

total, determination of 94 

Hazen's theorem 45 

Heat loss from the body, methods of 13 

Heat of combustion 117 

Hehner value 1 70 

Hehner's acid method for hardness 91 

Humidity 9 

determination of 22 

effect on heat loss of 14 

table of relative 210 

Hygrometer, hair 22 

Ice 55 

Imhoff tank 61 

Indicator, erythrosine 231 

methyl orange 231 

potassium chromate 84, 230 

Iodine value 171 

Hanus solution for 232 

Iron in water, determination of 89 

standard solution of 231 

Jackson's candle turbidimeter 95 

Kjeldahl method 183 

process for nitrogen in water 78 

reagents for 230 

Kubel's hot acid method 86 

Lead in water, determination of 97 

number of vanilla 202 

standard solution of 232 

Lemon color 207 

extract 205 

oil, determination of 206 

Lime water reagent for air analysis 38, 228 

Logwood test for alum in water 95 

Loss on ignition, determination of, in water 87 

Low's method for alum in water 96 



INDEX 247 

Page 

Silver nitrate solution 84, 230 

Skimmed milk, detection of 161 

Soap method for hardness 90 

solution, standard 231 

Soda reagent 93, 231 

Sodium carbonate, detection in milk : 154 

Sodium chloride solution, standard 84, 230 

thiosulphate solution, standard 232 

Solids of milk 140 

Sonden apparatus for air analysis 27 

Specific gravity of milk 139 

correction table 216 

solids 162 

wine 191 

Spoon test 177 

Standards for ammonia determination 75, 77 

Starch, determination of 186 

Steam vacuum method for air samples 25 

" Strippings " 138 

Sulphanilic acid 80, 229 

Sulphates in water, determination of 95 

table of 215 

Sulphites, detection of 198 

Sugars in cereal products . 185 

Surface waters 46 

Temperature, determination of 21 

effect on heat loss 13 

Tests on water, value of 67 

Thermometers, wet and dry bulb 22 

Turbidimeter for sulphates 95 

Turbidity, determination of 108 

Turmeric in lemon extract 207 

Typhoid fever 45 

Ultraviolet light for water sterilization 54 

Vanilla, adulteration of 200 

determination of 201 

extract 199 

Vapor tension of water, table of 208 

Ventilation 17 

formulae 18 

methods of 19 

Volatile acids, in wine 194 

Walker method for carbon dioxide 28 

Water, analytical methods 69 



248 INDEX 

Page 

Water, bacteriological examination of 57, 109 

chemical examination of 59, 67 

consumption 43 

cycle of 45 

daily quantity required 4 

ground , . . 48 

need of 3 

physiological action of 43 

purification of 51 

rain 45 

relation to disease 44 

safe 56 

necessity of 45 

samples, collection of 69 

sanitary examination of 57 

siphon method 24 

sterilization of 54 

storage of 46 

supplies, requirements for 56 

surface 46 

vapor in air, see Humidity. 

waste 43 

Waters, table of average composition of 211 

table of normal 212 

tables of polluted 213 

Wells, deep 49 

shallow 49 

Wine, composition of 190 

Winkler method for dissolved oxygen 100 



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